8-K 1 mab04op1_nov.txt NOVEMBER 8K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington D. C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 26, 2004 MASTR ASSET BACKED SECURITIES TRUST Mortgage Pass-Through Certificates, Series 2004-OPT1 Trust (Exact name of registrant as specified in its charter) New York (governing law of 333-106982-19 54-2150433 Pooling and Servicing Agreement) (Commission 54-2150434 (State or other File Number) IRS EIN jurisdiction of Incorporation) c/o Wells Fargo Bank, N.A. 9062 Old Annapolis Road Columbia, MD 21045 (Address of principal executive offices) (Zip Code) Registrant's telephone number, including area code: (410) 884-2000 (Former name or former address, if changed since last report) Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): [ ] Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) [ ] Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) [ ] Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act(17 CFR 240.14d-2(b)) [ ] Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act(17 CFR 240.13e-4(c)) ITEM 8.01 Other Events On November 26, 2004 a distribution was made to holders of MASTR ASSET BACKED SECURITIES TRUST, Mortgage Pass-Through Certificates, Series 2004-OPT1 Trust. ITEM 9.01 Financial Statements and Exhibits (c) Exhibits Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage Pass-Through Certificates, Series 2004-OPT1 Trust, relating to the November 26, 2004 distribution. Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. MASTR ASSET BACKED SECURITIES TRUST Mortgage Pass-Through Certificates, Series 2004-OPT1 Trust (Registrant) By: Wells Fargo Bank, N.A. as Trustee By: /s/ Beth Belfield as Assistant Vice President By: Beth Belfield as Assistant Vice President Date: 12/3/2004 INDEX TO EXHIBITS Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage Pass-Through Certificates, Series 2004-OP1 Trust, relating to the November 26, 2004 distribution. EX-99.1

MASTR Asset Backed Securitizations Mortgage Pass-Through Certificates Record Date: 810/31/2004 Distribution Date: 911/2726/2004 MABS Series: 2004-OP1 Contact: Customer Service - CTSLink Wells Fargo Bank, N.A. Securities Administration Services 7485 New Horizon Way Frederick, MD 21703 Telephone: (301) 815-6600 Fax: (301) 815-6660 Certificateholder Distribution Summary Certificate Certificate Beginning Class Pass-Through Certificate Interest Principal Class CUSIP Description Rate Balance Distribution Distribution A-1 57643LCE4 SEN 12.~~89500~~21250% ~~201~~182,~~516~~703,~~341~~331.7815 ~~350~~359,~~050~~316.6856 109,~~164~~424,~~795~~297.3651 A-2 57643LCF1 SEN 12.~~89500~~21250% ~~109~~99,~~758~~689,~~942~~934.3400 ~~190~~196,~~660~~056.4387 45,~~321~~414,~~757~~143.8107 A-3 57643LCG9 SEN 12.~~87500~~19250% ~~153~~138,~~200~~797,~~136~~490.4422 ~~263~~270,~~312~~500.7489 7,~~978~~326,~~029~~915.2243 M-1 57643LCH7 MEZ 2.~~13500~~45250% 42,151,000.00 8291,~~493~~889.0218 0.00 M-2 57643LCJ3 MEZ 23.~~71500~~03250% 34,333,000.00 8592,~~446~~546.2651 0.00 M-3 57643LCK0 MEZ 23.~~91500~~23250% 10,538,000.00 2830,~~158~~279.4119 0.00 M-4 57643LCL8 MEZ 3.~~16500~~48250% 8,158,000.00 2325,~~668~~253.4054 0.00 M-5 57643LCM6 MEZ 3.~~31500~~63250% 8,838,000.00 2628,~~856~~536.4792 0.00 M-6 57643LCN4 MEZ 4.~~36500~~68250% 6,799,000.00 2728,~~204~~298.5095 0.00 M-7 57643LCP9 MEZ 5.~~36500~~68250% 7,138,000.00 3536,~~104~~054.0983 0.00 CE MAB4OPT1C OC 0.00000% 7,818,296.32 2,~~411~~077,~~263~~399.4372 0.00 R MAB4OP1R2 RES 0.00000% 0.00 0.00 0.00 P MAB4OPT1P Pre-pay 0.00000% 100.00 ~~296~~309,~~475~~756.7600 0.00 Totals ~~590~~546,~~248~~964,~~816~~151.8869 3,~~820~~545,~~694~~889.1916 22,~~464~~165,~~582~~356.3901

Certificateholder Distribution Summary (continued) Current Ending Cumulative Realized Certificate Total Realized Class Loss Balance Distribution Losses A-1 0.00 ~~191~~173,~~351~~279,~~546~~033.4264 109,~~514~~783,~~846~~614.0407 0.00 A-2 0.00 ~~105~~94,~~437~~275,~~184~~790.5393 45,~~512~~610,~~418~~199.2494 0.00 A-3 0.00 ~~145~~131,~~222~~470,~~107~~574.2278 87,~~241~~597,~~341~~416.9632 0.00 M-1 0.00 42,151,000.00 8291,~~493~~889.0218 0.00 M-2 0.00 34,333,000.00 8592,~~446~~546.2651 0.00 M-3 0.00 10,538,000.00 2830,~~158~~279.4119 0.00 M-4 0.00 8,158,000.00 2325,~~668~~253.4054 0.00 M-5 0.00 8,838,000.00 2628,~~856~~536.4792 0.00 M-6 0.00 6,799,000.00 2728,~~204~~298.5095 0.00 M-7 0.00 7,138,000.00 3536,~~104~~054.0983 0.00 CE 0.00 7,818,296.32 2,~~411~~077,~~263~~399.4372 0.00 R 0.00 0.00 0.00 0.00 P 0.00 100.00 ~~296~~309,~~475~~756.7600 0.00 Totals 0.00 ~~567~~524,~~784~~798,~~234~~795.4967 2625,~~285~~711,~~276~~245.5817 0.00 All distributions required by the Pooling and Servicing Agreement have been calculated by the Certificate Administrator on behalf of the Trustee.

Principal Distribution Statement Original Beginning Scheduled Unscheduled Face Certificate Principal Principal Realized Class Amount Balance Distribution Distribution Accretion Loss (1) A-1 240,738,000.00 ~~201~~182,~~516~~703,~~341~~331.7815 0.00 109,~~164~~424,~~795~~297.3651 0.00 0.00 A-2 129,838,000.00 ~~109~~99,~~758~~689,~~942~~934.3400 0.00 45,~~321~~414,~~757~~143.8107 0.00 0.00 A-3 183,503,000.00 ~~153~~138,~~200~~797,~~136~~490.4422 0.00 7,~~978~~326,~~029~~915.2243 0.00 0.00 M-1 42,151,000.00 42,151,000.00 0.00 0.00 0.00 0.00 M-2 34,333,000.00 34,333,000.00 0.00 0.00 0.00 0.00 M-3 10,538,000.00 10,538,000.00 0.00 0.00 0.00 0.00 M-4 8,158,000.00 8,158,000.00 0.00 0.00 0.00 0.00 M-5 8,838,000.00 8,838,000.00 0.00 0.00 0.00 0.00 M-6 6,799,000.00 6,799,000.00 0.00 0.00 0.00 0.00 M-7 7,138,000.00 7,138,000.00 0.00 0.00 0.00 0.00 CE 7,817,754.23 7,818,296.32 0.00 0.00 0.00 0.00 R 0.00 0.00 0.00 0.00 0.00 0.00 P 100.00 100.00 0.00 0.00 0.00 0.00 Totals 679,851,854.23 ~~590~~546,~~248~~964,~~816~~151.8869 0.00 22,~~464~~165,~~582~~356.3901 0.00 0.00 (1) Amount Does Not Include Excess Special Hazard, Bankruptcy, or Fraud Losses Unless Otherwise Disclosed. Please Refer to the Prospectus Supplement for a Full Description.

Principal Distribution Statement (continued) Total Ending Ending Total Principal Certificate Certificate Principal Class Reduction Balance Percentage Distribution A-1 109,~~164~~424,~~795~~297.3651 ~~191~~173,~~351~~279,~~546~~033.4264 0.~~79485393~~71978264 109,~~164~~424,~~795~~297.3651 A-2 45,~~321~~414,~~757~~143.8107 ~~105~~94,~~437~~275,~~184~~790.5393 0.~~81206723~~72610323 45,~~321~~414,~~757~~143.8107 A-3 7,~~978~~326,~~029~~915.2243 ~~145~~131,~~222~~470,~~107~~574.2278 0.~~79138819~~71644918 7,~~978~~326,~~029~~915.2243 M-1 0.00 42,151,000.00 1.00000000 0.00 M-2 0.00 34,333,000.00 1.00000000 0.00 M-3 0.00 10,538,000.00 1.00000000 0.00 M-4 0.00 8,158,000.00 1.00000000 0.00 M-5 0.00 8,838,000.00 1.00000000 0.00 M-6 0.00 6,799,000.00 1.00000000 0.00 M-7 0.00 7,138,000.00 1.00000000 0.00 CE 0.00 7,818,296.32 1.00006934 0.00 R 0.00 0.00 0.00000000 0.00 P 0.00 100.00 1.00000000 0.00 Totals 22,~~464~~165,~~582~~356.3901 ~~567~~524,~~784~~798,~~234~~795.4967 0.~~83515876~~77193111 22,~~464~~165,~~582~~356.3901

Principal Distribution Factors Statement Original Beginning Scheduled Unscheduled Face Certificate Principal Principal Class (2) Amount Balance Distribution Distribution Accretion A-1 240,738,000.00 ~~837~~758.~~07741104~~93016952 0.00000000 4239.~~22347681~~14752764 0.00000000 A-2 129,838,000.00 ~~845~~767.~~35299635~~80244613 0.00000000 3341.~~28577004~~69921803 0.00000000 A-3 183,503,000.00 ~~834~~756.~~86447873~~37722664 0.00000000 4339.~~47628769~~92804167 0.00000000 M-1 42,151,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-2 34,333,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-3 10,538,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-4 8,158,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-5 8,838,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-6 6,799,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-7 7,138,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 CE 7,817,754.23 1000.06934089 0.00000000 0.00000000 0.00000000 R 0.00 0.00000000 0.00000000 0.00000000 0.00000000 P 100.00 1000.00000000 0.00000000 0.00000000 0.00000000 (2) All Classes are per $1,000 denomination

Principal Distribution Factors Statement (continued) Total Ending Ending Total Realized Principal Certificate Certificate Principal Class Loss (3) Reduction Balance Percentage Distribution A-1 0.00000000 4239.~~22347681~~14752764 ~~794~~719.~~85393424~~78264188 0.~~79485393~~71978264 4239.~~22347681~~14752764 A-2 0.00000000 3341.~~28577004~~69921803 ~~812~~726.~~06722631~~10322810 0.~~81206723~~72610323 3341.~~28577004~~69921803 A-3 0.00000000 4339.~~47628769~~92804167 ~~791~~716.~~38819104~~44918492 0.~~79138819~~71644918 4339.~~47628769~~92804167 M-1 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-2 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-3 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-4 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-5 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-6 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-7 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 CE 0.00000000 0.00000000 1,000.06934089 1.00006934 0.00000000 R 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 P 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 (3) Amount Does Not Include Excess Special Hazard, Bankruptcy, or Fraud Losses Unless Otherwise Disclosed. Please Refer to the Prospectus Supplement for a Full Description.

Interest Distribution Statement Beginning Payment of Original Current Certificate/ Current Unpaid Current Face Certificate Notional Accrued Interest Interest Class Amount Rate Balance Interest Shortfall Shortfall A-1 240,738,000.00 12.~~89500~~21250% ~~201~~182,~~516~~703,~~341~~331.7815 ~~350~~359,~~050~~316.6855 0.00 0.00 A-2 129,838,000.00 12.~~89500~~21250% ~~109~~99,~~758~~689,~~942~~934.3400 ~~190~~196,~~660~~056.4387 0.00 0.00 A-3 183,503,000.00 12.~~87500~~19250% ~~153~~138,~~200~~797,~~136~~490.4422 ~~263~~270,~~312~~500.7389 0.00 0.00 M-1 42,151,000.00 2.~~13500~~45250% 42,151,000.00 8291,~~493~~889.0218 0.00 0.00 M-2 34,333,000.00 23.~~71500~~03250% 34,333,000.00 8592,~~446~~546.2551 0.00 0.00 M-3 10,538,000.00 23.~~91500~~23250% 10,538,000.00 2830,~~158~~279.4119 0.00 0.00 M-4 8,158,000.00 3.~~16500~~48250% 8,158,000.00 2325,~~668~~253.4054 0.00 0.00 M-5 8,838,000.00 3.~~31500~~63250% 8,838,000.00 2628,~~856~~536.4792 0.00 0.00 M-6 6,799,000.00 4.~~36500~~68250% 6,799,000.00 2728,~~204~~298.5095 0.00 0.00 M-7 7,138,000.00 5.~~36500~~68250% 7,138,000.00 3536,~~104~~054.0983 0.00 0.00 CE 7,817,754.23 0.00000% 7,818,296.32 0.00 0.00 0.00 R 0.00 0.00000% 0.00 0.00 0.00 0.00 P 100.00 0.00000% 100.00 0.00 0.00 0.00 Totals 679,851,854.23 1,~~112~~158,~~954~~733.9843 0.00 0.00

Interest Distribution Statement (continued) Remaining Ending Non-Supported Total Unpaid Certificate/ Interest Realized Interest Interest Notional Class Shortfall Losses (4) Distribution Shortfall Balance A-1 (0.~~01)~~00 0.00 ~~350~~359,~~050~~316.6856 0.00 ~~191~~173,~~351~~279,~~546~~033.4264 A-2 0.00 0.00 ~~190~~196,~~660~~056.4387 0.00 ~~105~~94,~~437~~275,~~184~~790.5393 A-3 0.00 0.00 ~~263~~270,~~312~~500.7489 0.00 ~~145~~131,~~222~~470,~~107~~574.2278 M-1 0.00 0.00 8291,~~493~~889.0218 0.00 42,151,000.00 M-2 0.00 0.00 8592,~~446~~546.2651 0.00 34,333,000.00 M-3 0.00 0.00 2830,~~158~~279.4119 0.00 10,538,000.00 M-4 0.00 0.00 2325,~~668~~253.4054 0.00 8,158,000.00 M-5 0.00 0.00 2628,~~856~~536.4792 0.00 8,838,000.00 M-6 0.00 0.00 2728,~~204~~298.5095 0.00 6,799,000.00 M-7 0.00 0.00 3536,~~104~~054.0983 0.00 7,138,000.00 CE 0.00 0.00 2,~~411~~077,~~263~~399.4372 0.00 7,818,296.32 R 0.00 0.00 0.00 0.00 0.00 P 0.00 0.00 ~~296~~309,~~475~~756.7600 0.00 100.00 Totals (0.~~01)~~00 0.00 3,~~820~~545,~~694~~889.1916 0.00 (4) Amount Does Not Include Excess Special Hazard, Bankruptcy, or Fraud Losses Unless Otherwise Disclosed. Please Refer to the Prospectus Supplement for a Full Description.

Interest Distribution Factors Statement Beginning Payment of Original Current Certificate/ Current Unpaid Current Face Certificate Notional Accrued Interest Interest Class (5) Amount Rate Balance Interest Shortfall Shortfall A-1 240,738,000.00 12.~~89500~~21250% ~~837~~758.~~07741104~~93016952 1.~~45407322~~49256266 0.00000000 0.00000000 A-2 129,838,000.00 12.~~89500~~21250% ~~845~~767.~~35299635~~80244613 1.~~46844861~~51001148 0.00000000 0.00000000 A-3 183,503,000.00 12.~~87500~~19250% ~~834~~756.~~86447873~~37722664 1.~~43492330~~47409519 0.00000000 0.00000000 M-1 42,151,000.00 2.~~13500~~45250% 1000.00000000 12.~~95708334~~18000000 0.00000000 0.00000000 M-2 34,333,000.00 23.~~71500~~03250% 1000.00000000 2.~~48874989~~69555559 0.00000000 0.00000000 M-3 10,538,000.00 23.~~91500~~23250% 1000.00000000 2.~~67208294~~87333365 0.00000000 0.00000000 M-4 8,158,000.00 3.~~16500~~48250% 1000.00000000 23.~~90125031~~09555528 0.00000000 0.00000000 M-5 8,838,000.00 3.~~31500~~63250% 1000.00000000 3.~~03874972~~22888889 0.00000000 0.00000000 M-6 6,799,000.00 4.~~36500~~68250% 1000.00000000 4.~~00125018~~16222239 0.00000000 0.00000000 M-7 7,138,000.00 5.~~36500~~68250% 1000.00000000 45.~~91791678~~05111096 0.00000000 0.00000000 CE 7,817,754.23 0.00000% 1000.06934089 0.00000000 0.00000000 0.00000000 R 0.00 0.00000% 0.00000000 0.00000000 0.00000000 0.00000000 P 100.00 0.00000% 1000.00000000 0.00000000 0.00000000 0.00000000 (5) All Classes are per $1,000 denomination

Interest Distribution Factors Statement (continued) Remaining Ending Non-Supported Total Unpaid Certificate/ Interest Realized Interest Interest Notional Class Shortfall Losses (6) Distribution Shortfall Balance A-1 (0.~~00000004)~~00000000 0.00000000 1.~~45407322~~49256270 0.00000000 ~~794~~719.~~85393424~~78264188 A-2 0.00000000 0.00000000 1.~~46844861~~51001148 0.00000000 ~~812~~726.~~06722631~~10322810 A-3 0.00000000 0.00000000 1.~~43492335~~47409519 0.00000000 ~~791~~716.~~38819104~~44918492 M-1 0.00000000 0.00000000 12.~~95708334~~18000000 0.00000000 1000.00000000 M-2 0.00000000 0.00000000 2.~~48875018~~69555559 0.00000000 1000.00000000 M-3 0.00000000 0.00000000 2.~~67208294~~87333365 0.00000000 1000.00000000 M-4 0.00000000 0.00000000 23.~~90125031~~09555528 0.00000000 1000.00000000 M-5 0.00000000 0.00000000 3.~~03874972~~22888889 0.00000000 1000.00000000 M-6 0.00000000 0.00000000 4.~~00125018~~16222239 0.00000000 1000.00000000 M-7 0.00000000 0.00000000 45.~~91791678~~05111096 0.00000000 1000.00000000 CE 0.00000000 0.00000000 ~~308~~265.~~43428420~~72845077 0.00000000 1000.06934089 R 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 P 0.00000000 0.00000000 ~~2964757~~3097560.~~60000000~~00000000 0.00000000 1000.00000000 (6) Amount Does Not Include Excess Special Hazard, Bankruptcy,or Fraud Losses Unless Otherwise Disclosed. Please Refer to the Prospectus Supplement for a Full Description.

CERTIFICATEHOLDER ACCOUNT STATEMENT CERTIFICATE ACCOUNT Beginning Balance 0.00 Deposits Payments of Interest and Principal 2625,~~139~~566,~~841~~908.1677 Liquidations, Insurance Proceeds, Reserve Funds 0.00 Proceeds from Repurchased Loans 0.00 Other Amounts (Servicer Advances) 0.00 Realized Loss (Gains, Subsequent Expenses & Recoveries) ~~456~~(25,032.8815) Prepayment Penalties ~~296~~309,~~475~~756.7600 Total Deposits 2625,~~436~~851,~~773~~632.8062 Withdrawals Reimbursement for Servicer Advances 0.00 Payment of Service Fee ~~151~~140,~~497~~387.2245 Payment of Interest and Principal 2625,~~285~~711,~~276~~245.5817 Total Withdrawals (Pool Distribution Amount) 2625,~~436~~851,~~773~~632.8062 Ending Balance 0.00

SERVICING FEES Gross Servicing Fee ~~147~~136,~~562~~741.2303 Trustee Fee -Wells Fargo Bank, NA 3,~~934~~646.9942 Supported Prepayment/Curtailment Interest Shortfall 0.00 Net Servicing Fee ~~151~~140,~~497~~387.2245

LOAN STATUS STRATIFICATION/CREDIT ENHANCEMENT STATEMENT DELINQUENCY STATUS DELINQUENT BANKRUPTCY FORECLOSURE REO Total No of Loans No of Loans No of Loans No of Loans No of Loans Principal Balance Principal Balance Principal Balance Principal Balance Principal Balance 0-29 Days 108 20 0 128 1,~~041~~177,~~271~~914.7949 ~~466,265~~0.7400 0.00 1,~~507~~177,~~537~~914.5349 30 Days 5269 10 12 0 5471 79,~~841~~687,~~709~~745.4349 ~~235,959~~0.4900 ~~278~~467,~~241~~571.8427 0.00 810,~~355~~155,~~910~~316.76 60 Days 2321 01 57 0 2829 3,~~743~~426,~~402~~845.7584 080,479.0075 1,~~021~~757,~~258~~257.8213 0.00 45,~~764~~264,~~661~~582.5772 90 Days 1219 34 2640 32 4465 13,~~995~~171,~~920~~350.1932 ~~275~~559,~~420~~942.9353 35,~~613~~989,~~883~~220.3486 ~~325~~233,~~684~~725.5872 69,~~210~~954,~~909~~239.0443 120 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 150 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 180+ Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 Totals 87109 1413 3449 32 ~~138~~173 1316,~~581~~285,~~032~~941.3765 1,~~552~~818,~~652~~336.2177 58,~~379~~214,~~649~~049.7426 ~~325~~233,~~684~~725.5872 2026,~~839~~552,~~018~~053.9040 No of Loans No of Loans No of Loans No of Loans No of Loans Principal Balance Principal Balance Principal Balance Principal Balance Principal Balance 0-29 Days 0.~~267380~~229753% 0.~~053476~~000000% 0.000000% 0.~~320856~~229753% 0.~~183327~~224354% 0.~~082091~~000000% 0.000000% 0.~~265418~~224354% 30 Days 1.~~390374~~981620% 0.~~026738~~000000% 0.~~026738~~057438% 0.000000% 12.~~443850~~039058% 1.~~380617~~845194% 0.~~041543~~000000% 0.~~048987~~089057% 0.000000% 1.~~471147~~934251% 60 Days 0.~~614973~~603102% 0.~~000000~~028719% 0.~~133690~~201034% 0.000000% 0.~~748663~~832855% 0.~~659066~~652700% 0.~~000000~~015329% 0.~~179804~~334699% 0.000000% 01.~~838870~~002728% 90 Days 0.~~320856~~545663% 0.~~080214~~114877% 01.~~695187~~148765% 0.~~080214~~057438% 1.~~176471~~866743% 0.~~351403~~604037% 0.~~048491~~106650% 01.~~636263~~140748% 0.~~057340~~044517% 1.~~093497~~895952% 120 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 150 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 180+ Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% Totals 23.~~326203~~130385% 0.~~374332~~373349% 01.~~909091~~407237% 0.~~080214~~057438% 34.~~689840~~968409% 23.~~391086~~101931% 0.~~273361~~346333% 01.~~947145~~564504% 0.~~057340~~044517% 35.~~668932~~057285% (7) Delinquencies are stratified according to the informationthe Servicer has provided. All 90+ are reporting the 90 day delinquency field.

OTHER INFORMATION Current Period Class A Insufficient Funds 0.00 Principal Balance of Contaminated Properties 0.00 Periodic Advance ~~247~~276,~~523~~805.6818 Class M-1 83,621,854.23 12.30001120% 83,622,396.32 1415.~~72784752~~93418221% 78.~~423771~~031840% 0.000000% Class M-2 49,288,854.23 7.24994040% 49,289,396.32 89.~~68100826~~39205591% 6.~~046839~~542126% 0.000000% Class M-3 38,750,854.23 5.69989682% 38,751,396.32 67.~~82502154~~38404826% 12.~~855987~~008008% 0.000000% Class M-4 30,592,854.23 4.49992951% 30,593,396.32 5.~~38820814~~82954774% 1.~~436813~~554501% 0.000000% Class CE 100.00 0.00001471% 100.00 0.~~00001761~~00001905% 1.~~376984~~489770% 0.000000% Class R-II 100.00 0.00001471% 100.00 0.~~00001761~~00001905% 0.000000% 0.000000% Class P 0.00 0.00000000% 0.00 0.00000000% 0.~~000018~~000019% 0.000000% Please Refer to the Prospectus Supplement for a Full Description of Loss Exposure

COLLATERAL STATEMENT Collateral Description Mixed Fixed & Arm Weighted Average Gross Coupon 7.~~471951~~462762% Weighted Average Net Coupon 7.~~171951~~162762% Weighted Average Pass-Through Rate 7.~~163951~~154762% Weighted Average Maturity(Stepdown Calculation ) ~~346~~344 Beginning Scheduled Collateral Loan Count 3,~~858~~618 Number Of Loans Paid In Full ~~118~~136 Ending Scheduled Collateral Loan Count 3,~~740~~482 Beginning Scheduled Collateral Balance ~~590~~546,~~248~~964,~~816~~151.8969 Ending Scheduled Collateral Balance ~~567~~524,~~784~~798,~~234~~795.4968 Ending Actual Collateral Balance at 31-~~Aug~~Oct-2004 ~~567~~525,~~985~~025,~~964~~852.7997 Monthly P &I Constant 43,~~181~~880,~~756~~322.1026 Special Servicing Fee 0.00 Prepayment Penalties ~~296~~309,~~475~~756.7600 Realized Loss Amount ~~(456~~25,032.~~88)~~15 Cumulative Realized Loss 429,~~259~~211.2984 Ending Scheduled Balance for Premium Loans ~~567~~524,~~784~~798,~~234~~795.4968 Scheduled Principal ~~506~~478,~~497~~769.3551 Unscheduled Principal 21,~~958~~686,~~085~~586.0550

Miscellaneous Reporting Net Monthly Excess Cashflow 2,~~410~~102,~~806~~431.8487 Extra Principal Ditribution Amount ~~-456~~25,032.8883 OC Amount 7,818,~~297~~296.0032 OC Deficiency Amount 025,032.0083 OC Release Amount ~~-456~~0.8800 OC Target Amount 7,818,~~297~~296.0032 Stepdown NO Trigger Event NO Credit Enhancement Percentage 2122.~~208523~~994797%

Group Level Collateral Statement Group Group 1 Group 2 Group 3 Collateral Description Fixed 15/30 & ARM Fixed 15/30 & ARM Fixed 15/30 & ARM Weighted Average Coupon Rate 7.~~575743~~584840 9.~~464983~~465089 7.~~518296~~502939 Weighted Average Net Rate 7.~~275743~~284840 9.~~164988~~165100 7.~~218296~~202939 Weighted Average Maturity ~~346~~344 ~~346~~344 ~~346~~344 Beginning Loan Count ~~715~~685 3 1,~~126~~041 Loans Paid In Full 1118 0 4946 Ending Loan Count ~~704~~667 3 ~~1,077~~995 Beginning Scheduled Balance 9591,~~778~~476,~~319~~162.0334 ~~256~~255,~~243~~969.8871 ~~160~~145,~~129~~618,~~610~~791.9033 Ending scheduled Balance 9488,~~315~~703,~~224~~189.7956 ~~256~~255,~~107~~831.3302 ~~151~~138,~~427~~978,~~839~~248.6050 Record Date 0810/31/2004 0810/31/2004 0810/31/2004 Principal And Interest Constant ~~696~~666,~~538~~630.0173 2,157.67 1,~~126~~025,~~049~~283.7396 Scheduled Principal 9188,~~878~~437.0834 ~~136~~138.5569 ~~122~~114,~~798~~809.2887 Unscheduled Principal 12,~~371~~684,~~216~~535.1644 0.00 86,~~578~~525,~~973~~732.0296 Scheduled Interest ~~604~~578,~~659~~193.9339 2,~~021~~018.1298 1910,~~003,251~~474.4509 Servicing Fees 2322,~~944~~869.5904 6463.0699 4036,~~032~~404.3871 Master Servicing Fees 0.00 0.00 0.00 Trustee Fee ~~638~~609.5386 1.71 ~~1,067~~970.5679 FRY Amount 0.00 0.00 0.00 Special Hazard Fee 0.00 0.00 0.00 Other Fee 0.00 0.00 0.00 Pool Insurance Fee 0.00 0.00 0.00 Spread Fee 1 0.00 0.00 0.00 Spread Fee 2 0.00 0.00 0.00 Spread Fee 3 0.00 0.00 0.00 Net Interest ~~580~~554,~~076~~714.8149 1,~~955~~953.3528 ~~962~~873,~~151~~098.5159 Realized Loss Amount 0.00 0.00 0.00 Cumulative Realized Loss 0.00 0.00 0.00 Percentage of Cumulative Losses 0.0000 0.0000 0.0000 Prepayment Penalties 0.00 0.00 0.00 Special Servicing Fee 0.00 0.00 0.00 Pass-Through Rate 7.~~267743~~276840 9.~~156983~~157089 7.~~210296~~194939

Group Level Collateral Statement Group Group 4 Group 5 Group 6 Collateral Description Fixed 15/30 & ARM Fixed 15/30 & ARM Fixed 15/30 & ARM Weighted Average Coupon Rate 7.~~580028~~564475 8.~~114026~~114210 7.~~461849~~442854 Weighted Average Net Rate 7.~~280028~~264475 7.~~814027~~814225 7.~~161849~~142854 Weighted Average Maturity ~~346~~344 ~~346~~344 ~~346~~344 Beginning Loan Count ~~380~~369 4 ~~573~~521 Loans Paid In Full 314 0 2422 Ending Loan Count ~~377~~355 4 ~~549~~499 Beginning Scheduled Balance 5250,~~622~~745,~~855~~907.6003 305,~~880~~415.7131 8678,~~304~~112,~~244~~540.4420 Ending scheduled Balance 5148,~~999~~683,~~089~~837.6793 305,~~662~~163.9422 8274,~~606~~741,~~382~~800.4356 Record Date 0810/31/2004 0810/31/2004 0810/31/2004 Principal And Interest Constant ~~380~~366,~~602~~046.6604 2,286.04 ~~605~~547,~~434~~879.7407 Scheduled Principal 4846,~~200~~157.3959 ~~217~~220.7787 6863,~~777~~395.0655 Unscheduled Principal ~~575~~2,~~565~~015,911.5451 031.0022 3,~~629~~307,~~084~~344.9509 Scheduled Interest ~~332~~319,~~402~~888.2745 2,~~068~~065.2717 ~~536~~484,~~657~~483.6852 Servicing Fees 1312,~~155~~686.7347 76.4735 2119,~~576~~528.0614 Master Servicing Fees 0.00 0.00 0.00 Trustee Fee ~~350~~338.8129 2.04 ~~575~~520.3677 FRY Amount 0.00 0.00 0.00 Special Hazard Fee 0.00 0.00 0.00 Other Fee 0.00 0.00 0.00 Pool Insurance Fee 0.00 0.00 0.00 Spread Fee 1 0.00 0.00 0.00 Spread Fee 2 0.00 0.00 0.00 Spread Fee 3 0.00 0.00 0.00 Net Interest ~~318~~306,~~895~~863.7369 1,~~989~~986.7678 ~~514~~464,~~506~~434.2661 Realized Loss Amount 0.00 0.00 025,032.0015 Cumulative Realized Loss 0.00 0.00 025,032.0015 Percentage of Cumulative Losses 0.0000 0.0000 0.~~0000~~0243 Prepayment Penalties 0.00 0.00 0.00 Special Servicing Fee 0.00 0.00 0.00 Pass-Through Rate 7.~~272028~~256475 7.~~806026~~806210 7.~~153849~~134854

Group Level Collateral Statement Group Group 7 Group 8 Group 9 Collateral Description Fixed 15/30 & ARM Fixed 15/30 & ARM Fixed 15/30 & ARM Weighted Average Coupon Rate 7.~~374040~~339067 6.~~699999~~700040 7.~~339045~~349785 Weighted Average Net Rate 7.~~074039~~039067 6.~~399966~~399977 7.~~039045~~049785 Weighted Average Maturity ~~344~~342.00 ~~344~~342.00 ~~344~~342.00 Record Date 0810/31/2004 0810/31/2004 0810/31/2004 Principal And Interest Constant ~~630~~595,~~377~~107.5427 597.83 ~~737~~674,~~711~~333.8865 Beginning Loan Count ~~511~~487 1 ~~545~~507 Loans Paid In Full 1116 0 20 Ending Loan Count ~~500~~471 1 ~~525~~487 Beginning Scheduled Balance 8782,~~763~~987,~~958~~226.9866 91,~~989~~820.8695 ~~106~~97,~~995~~370,~~713~~318.4916 Ending Scheduled Balance 8580,~~760~~408,~~262~~566.9683 91,~~905~~735.6479 ~~101~~92,~~021~~630,~~759~~422.1327 Scheduled Principal 9187,~~065~~566.1257 8485.2216 8377,~~339~~957.8887 Unscheduled Principal 12,~~912~~491,~~630~~093.9026 0.00 54,~~890~~661,~~614~~938.4802 Scheduled Interest ~~539~~507,~~312~~540.4270 ~~513~~512.6167 ~~654~~596,~~372~~375.0078 Servicing Fee 2120,~~941~~746.0180 2322.0096 2624,~~748~~342.9357 Master Servicing Fee 0.00 0.00 0.00 Trustee Fee ~~585~~553.0621 0.61 ~~713~~649.3114 Fry Amount 0.00 0.00 0.00 Special Hazard Fee 0.00 0.00 0.00 Other Fee 0.00 0.00 0.00 Pool Insurance Fee 0.00 0.00 0.00 Spread 1 0.00 0.00 0.00 Spread 2 0.00 0.00 0.00 Spread 3 0.00 0.00 0.00 Net Interest ~~516~~486,~~786~~240.3569 ~~490~~489.0010 ~~626~~571,~~909~~384.7607 Realized Loss Amount 0.00 0.00 ~~(456~~0.~~88)~~00 Cumulative Realized Loss 0.00 0.00 4,~~259~~179.2969 Percentage of Cumulative Losses 0.0000 0.0000 0.~~0033~~0032 Prepayment Penalties 0.00 0.00 0.00 Special Servicing Fee 0.00 0.00 0.00 Pass-Through Rate 7.~~066040~~031067 6.~~391999~~392040 7.~~031045~~041785

Group Level Collateral Statement Group Total Collateral Description Mixed Fixed & Arm Weighted Average Coupon Rate 7.~~471951~~462762 Weighted Average Net Rate 7.~~171951~~162762 Weighted Average Maturity ~~346~~344.00 Record Date 0810/31/2004 Principal And Interest Constant 43,~~181~~880,~~756~~322.1026 Beginning Loan Count 3,~~858~~618 Loans Paid In Full ~~118~~136 Ending Loan Count 3,~~740~~482 Beginning Scheduled Balance ~~590~~546,~~248~~964,~~816~~151.8969 Ending Scheduled Balance ~~567~~524,~~784~~798,~~234~~795.4968 Scheduled Principal ~~506~~478,~~497~~769.3551 Unscheduled Principal 21,~~958~~686,~~085~~586.0550 Scheduled Interest 3,~~675~~401,~~258~~552.75 Servicing Fee ~~147~~136,~~562~~741.2303 Master Servicing Fee 0.00 Trustee Fee 3,~~934~~646.9942 Fry Amount 0.00 Special Hazard Fee 0.00 Other Fee 0.00 Pool Insurance Fee 0.00 Spread 1 0.00 Spread 2 0.00 Spread 3 0.00 Net Interest 3,~~523~~261,~~761~~165.5330 Realized Loss Amount ~~(456~~25,032.~~88)~~15 Cumulative Realized Loss 429,~~259~~211.2984 Percentage of Cumulative Losses 0.~~0006~~0043 Prepayment Penalties 0.00 Special Servicing Fee 0.00 Pass-Through Rate 7.~~163951~~154762

Filing Compare · MASTR ASSET BACKED SECURITIES TRUST 2004-OPT1