8-K 1 mab03op1_dec.txt DECEMBER 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): December 26, 2003 MASTR ASSET BACKED SECURITIES TRUST Mortgage Pass-Through Certificates, Series 2003-OP1 Trust (Exact name of registrant as specified in its charter) New York (governing law of 333-75724-15 Pooling and Servicing Agreement) (Commission 54-2102390 (State or other File Number) 54-2102389 jurisdiction IRS EIN of Incorporation) c/o Wells Fargo Bank Minnesota, 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) ITEM 5. Other Events On December 26, 2003 a distribution was made to holders of MASTR ASSET BACKED SECURITIES TRUST, Mortgage Pass-Through Certificates, Series 2003-OP1 Trust. ITEM 7. Financial Statements and Exhibits (c) Exhibits furnished in accordance with Item 601(a) of Regulation S-K Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage Pass-Through Certificates, Series 2003-OP1 Trust, relating to the December 26, 2003 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 2003-OP1 Trust By: Wells Fargo Bank Minnesota, N.A. as Trustee By: /s/ Beth Belfield as Assistant Vice President By: Beth Belfield as Assistant Vice President Date: 1/8/04 INDEX TO EXHIBITS Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage Pass-Through Certificates, Series 2003-OP1 Trust, relating to the December 26, 2003 distribution. EX-99.1

MASTR Asset Backed Securitizations Mortgage Pass-Through Certificates Record Date: 911/30/03 Distribution Date: 1012/2726/03 MABS Series: 2003-OP1 Contact: Customer Service - CTSLink Wells Fargo Bank Minnesota, 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 57643LAQ9 SEN 2.~~12000~~11875% ~~797~~708,~~557~~395,~~872~~043.2536 1,~~502~~292,~~953~~452.5000 4342,~~079~~086,~~160~~975.8170 A-2 57643LAJ5 SEN 1.~~54000~~53875% ~~302~~273,~~878~~591,~~815~~470.5838 ~~414~~362,~~607~~518.4520 1118,~~990~~870,~~682~~706.5062 M-1 57643LAK2 MEZ 1.~~97000~~96875% 58,600,000.00 ~~102~~99,~~615~~345.1131 0.00 M-2 57643LAL0 MEZ 2.~~97000~~96875% 51,275,000.00 ~~135~~131,~~366~~080.0062 0.00 M-3 57643LAM8 MEZ 3.~~87000~~86875% 21,975,000.00 7573,~~594~~208.0003 0.00 M-4 57643LAN6 MEZ 5.~~02000~~01875% 18,313,000.00 8179,~~716~~143.6832 0.00 MV-5 57643LAP1 MEZ 4.~~62000~~61875% 4,650,000.00 1918,~~096~~494.0024 0.00 MF-5 57643LAR7 MEZ 6.00000% 10,000,000.00 50,000.00 0.00 CE MAB03OP1C OC 0.00000% 10,980,010.85 4,~~824~~390,~~040~~688.2346 0.00 R-I MAB03OPR1 RES 0.00000% 0.00 0.00 0.00 R-II MAB03OPR2 RES 0.00000% 0.00 0.00 0.00 P MAB03OPTP Pre_Pay 0.00000% 100.00 1,~~128~~121,~~677~~299.4455 0.00 Totals 1,~~276~~157,~~229~~779,~~798~~624.6859 87,~~334~~618,~~666~~229.4173 5560,~~069~~957,~~843~~682.3132

Certificateholder Distribution Summary (continued) Current Ending Cumulative Realized Certificate Total Realized Class Loss Balance Distribution Losses A-1 0.00 ~~754~~666,~~478~~308,~~711~~067.4466 4443,~~582~~379,~~114~~427.3170 0.00 A-2 0.00 ~~290~~254,~~888~~720,~~133~~763.0776 1219,~~405~~233,~~289~~224.9582 0.00 M-1 0.00 58,600,000.00 ~~102~~99,~~615~~345.1131 0.00 M-2 0.00 51,275,000.00 ~~135~~131,~~366~~080.0062 0.00 M-3 0.00 21,975,000.00 7573,~~594~~208.0003 0.00 M-4 0.00 18,313,000.00 8179,~~716~~143.6832 0.00 MV-5 0.00 4,650,000.00 1918,~~096~~494.0024 0.00 MF-5 0.00 10,000,000.00 50,000.00 0.00 CE 0.00 10,980,010.85 4,~~824~~390,~~040~~688.2346 0.00 R-I 0.00 0.00 0.00 0.00 R-II 0.00 0.00 0.00 0.00 P 0.00 100.00 1,~~128~~121,~~677~~299.4455 0.00 Totals 0.00 1,~~221~~096,~~159~~821,~~955~~942.3627 6368,~~404~~575,~~509~~912.7205 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-1 939,100,000.00 ~~797~~708,~~557~~395,~~872~~043.2536 0.00 4342,~~079~~086,~~160~~975.8170 0.00 0.00 A-2 349,107,000.00 ~~302~~273,~~878~~591,~~815~~470.5838 0.00 1118,~~990~~870,~~682~~706.5062 0.00 0.00 M-1 58,600,000.00 58,600,000.00 0.00 0.00 0.00 0.00 M-2 51,275,000.00 51,275,000.00 0.00 0.00 0.00 0.00 M-3 21,975,000.00 21,975,000.00 0.00 0.00 0.00 0.00 M-4 18,313,000.00 18,313,000.00 0.00 0.00 0.00 0.00 MV-5 4,650,000.00 4,650,000.00 0.00 0.00 0.00 0.00 MF-5 10,000,000.00 10,000,000.00 0.00 0.00 0.00 0.00 CE 10,981,347.20 10,980,010.85 0.00 0.00 0.00 0.00 R-I 0.00 0.00 0.00 0.00 0.00 0.00 R-II 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 1,464,001,447.20 1,~~276~~157,~~229~~779,~~798~~624.6859 0.00 5560,~~069~~957,~~843~~682.3132 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 4342,~~079~~086,~~160~~975.8170 ~~754~~666,~~478~~308,~~711~~067.4466 0.~~80340615~~70951770 4342,~~079~~086,~~160~~975.8170 A-2 1118,~~990~~870,~~682~~706.5062 ~~290~~254,~~888~~720,~~133~~763.0776 0.~~83323489~~72963522 1118,~~990~~870,~~682~~706.5062 M-1 0.00 58,600,000.00 1.00000000 0.00 M-2 0.00 51,275,000.00 1.00000000 0.00 M-3 0.00 21,975,000.00 1.00000000 0.00 M-4 0.00 18,313,000.00 1.00000000 0.00 MV-5 0.00 4,650,000.00 1.00000000 0.00 MF-5 0.00 10,000,000.00 1.00000000 0.00 CE 0.00 10,980,010.85 0.99987831 0.00 R-I 0.00 0.00 0.00000000 0.00 R-II 0.00 0.00 0.00000000 0.00 P 0.00 100.00 1.00000000 0.00 Totals 5560,~~069~~957,~~843~~682.3132 1,~~221~~096,~~159~~821,~~955~~942.3627 0.~~83412483~~74919458 5560,~~069~~957,~~843~~682.3132

Principal Distribution Factors Statement Original Beginning Scheduled Unscheduled Face Certificate Principal Principal Class (2) Amount Balance Distribution Distribution Accretion A-1 939,100,000.00 ~~849~~754.~~27896097~~33398292 0.00000000 4544.~~87281526~~81628762 0.00000000 A-2 349,107,000.00 ~~867~~783.~~58161704~~68944301 0.00000000 3454.~~34672608~~05422011 0.00000000 M-1 58,600,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-2 51,275,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-3 21,975,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-4 18,313,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 MV-5 4,650,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 MF-5 10,000,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 CE 10,981,347.20 999.87830728 0.00000000 0.00000000 0.00000000 R-I 0.00 0.00000000 0.00000000 0.00000000 0.00000000 R-II 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 $1000 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 4544.~~87281526~~81628762 ~~803~~709.~~40614571~~51769530 0.~~80340615~~70951770 4544.~~87281526~~81628762 A-2 0.00000000 3454.~~34672608~~05422011 ~~833~~729.~~23489094~~63522290 0.~~83323489~~72963522 3454.~~34672608~~05422011 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 MV-5 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 MF-5 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 CE 0.00000000 0.00000000 999.87830728 0.99987831 0.00000000 R-I 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 R-II 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-1 939,100,000.00 2.~~12000~~11875% ~~797~~708,~~557~~395,~~872~~043.2536 1,~~502~~292,~~953~~452.5000 0.00 0.00 A-2 349,107,000.00 1.~~54000~~53875% ~~302~~273,~~878~~591,~~815~~470.5838 ~~414~~362,~~607~~518.4520 0.00 0.00 M-1 58,600,000.00 1.~~97000~~96875% 58,600,000.00 ~~102~~99,~~615~~345.1131 0.00 0.00 M-2 51,275,000.00 2.~~97000~~96875% 51,275,000.00 ~~135~~131,~~366~~080.0062 0.00 0.00 M-3 21,975,000.00 3.~~87000~~86875% 21,975,000.00 7573,~~594~~208.0003 0.00 0.00 M-4 18,313,000.00 5.~~02000~~01875% 18,313,000.00 8179,~~716~~143.6832 0.00 0.00 MV-5 4,650,000.00 4.~~62000~~61875% 4,650,000.00 1918,~~096~~494.0024 0.00 0.00 MF-5 10,000,000.00 6.00000% 10,000,000.00 50,000.00 0.00 0.00 CE 10,981,347.20 0.00000% 10,980,010.85 0.00 0.00 0.00 R-I 0.00 0.00000% 0.00 0.00 0.00 0.00 R-II 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 1,464,001,447.20 2,~~381~~106,~~948~~241.7472 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 0.00 0.00 1,~~502~~292,~~953~~452.5000 0.00 ~~754~~666,~~478~~308,~~711~~067.4466 A-2 0.00 0.00 ~~414~~362,~~607~~518.4520 0.00 ~~290~~254,~~888~~720,~~133~~763.0776 M-1 0.00 0.00 ~~102~~99,~~615~~345.1131 0.00 58,600,000.00 M-2 0.00 0.00 ~~135~~131,~~366~~080.0062 0.00 51,275,000.00 M-3 0.00 0.00 7573,~~594~~208.0003 0.00 21,975,000.00 M-4 0.00 0.00 8179,~~716~~143.6832 0.00 18,313,000.00 MV-5 0.00 0.00 1918,~~096~~494.0024 0.00 4,650,000.00 MF-5 0.00 0.00 50,000.00 0.00 10,000,000.00 CE 0.00 0.00 4,~~824~~390,~~040~~688.2346 0.00 10,980,010.85 R-I 0.00 0.00 0.00 0.00 0.00 R-II 0.00 0.00 0.00 0.00 0.00 P 0.00 0.00 1,~~128~~121,~~677~~299.4455 0.00 100.00 Totals 0.00 0.00 87,~~334~~618,~~666~~229.4173 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-1 939,100,000.00 2.~~12000~~11875% ~~849~~754.~~27896097~~33398292 1.~~60041902~~37626664 0.00000000 0.00000000 A-2 349,107,000.00 1.~~54000~~53875% ~~867~~783.~~58161704~~68944301 1.~~18762285~~03841573 0.00000000 0.00000000 M-1 58,600,000.00 1.~~97000~~96875% 1000.00000000 1.~~75111109~~69531246 0.00000000 0.00000000 M-2 51,275,000.00 2.~~97000~~96875% 1000.00000000 2.~~64000000~~55642360 0.00000000 0.00000000 M-3 21,975,000.00 3.~~87000~~86875% 1000.00000000 3.~~44000000~~33142344 0.00000000 0.00000000 M-4 18,313,000.00 5.~~02000~~01875% 1000.00000000 4.~~46222246~~32170152 0.00000000 0.00000000 MV-5 4,650,000.00 4.~~62000~~61875% 1000.00000000 43.~~10666667~~97725591 0.00000000 0.00000000 MF-5 10,000,000.00 6.00000% 1000.00000000 5.00000000 0.00000000 0.00000000 CE 10,981,347.20 0.00000% 999.87830728 0.00000000 0.00000000 0.00000000 R-I 0.00 0.00000% 0.00000000 0.00000000 0.00000000 0.00000000 R-II 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 $1000 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 0.00000000 0.00000000 1.~~60041902~~37626664 0.00000000 ~~803~~709.~~40614571~~51769530 A-2 0.00000000 0.00000000 1.~~18762285~~03841573 0.00000000 ~~833~~729.~~23489094~~63522290 M-1 0.00000000 0.00000000 1.~~75111109~~69531246 0.00000000 1000.00000000 M-2 0.00000000 0.00000000 2.~~64000000~~55642360 0.00000000 1000.00000000 M-3 0.00000000 0.00000000 3.~~44000000~~33142344 0.00000000 1000.00000000 M-4 0.00000000 0.00000000 4.~~46222246~~32170152 0.00000000 1000.00000000 MV-5 0.00000000 0.00000000 43.~~10666667~~97725591 0.00000000 1000.00000000 MF-5 0.00000000 0.00000000 5.00000000 0.00000000 1000.00000000 CE 0.00000000 0.00000000 ~~439~~399.~~29402669~~83149426 0.00000000 999.87830728 R-I 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 R-II 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 P 0.00000000 0.00000000 ~~11286774~~11212995.~~40000000~~50000000 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 6368,~~692~~796,~~865~~356.3483 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) (4088,~~742~~007.1274) Prepayment Penalties 1,~~128~~121,~~677~~299.4455 Total Deposits 6469,~~780~~829,~~800~~648.6664 Withdrawals Reimbursement for Servicer Advances 0.00 Payment of Service Fee 1,~~376~~253,~~290~~736.9459 Payment of Interest and Principal 6368,~~404~~575,~~509~~912.7205 Total Withdrawals (Pool Distribution Amount) 6469,~~780~~829,~~800~~648.6664 Ending Balance 0.00

SERVICING FEES Gross Servicing Fee ~~531~~482,~~762~~408.2908 Radian ~~841~~768,~~337~~433.0544 Trustee Fee - Wells Fargo 32,~~191~~895.6007 Supported Prepayment/Curtailment Interest Shortfall 0.00 Net Servicing Fee 1,~~376~~253,~~290~~736.9459

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 3836 20 0 4036 54,~~023~~554,~~536~~551.2603 ~~192,308~~0.1900 0.00 54,~~215~~554,~~844~~551.4503 30 Days ~~135~~124 20 34 0 ~~140~~128 1817,~~793~~612,~~970~~389.3237 ~~142,241~~0.7900 ~~401~~417,~~579~~265.9959 0.00 1918,~~337~~029,~~792~~654.1096 60 Days 2022 5 4849 0 7376 24,~~743~~020,~~695~~084.6187 ~~497~~398,~~471~~743.1568 6,~~675~~462,~~079~~669.4280 0.00 910,~~916~~881,~~246~~498.1835 90 Days 1413 4359 ~~161~~210 1223 ~~230~~305 1,~~396~~457,~~402~~619.5653 56,~~290~~829,~~881~~769.0788 2330,~~692~~634,~~048~~729.9294 12,~~151~~218,~~934~~555.8699 3141,~~531~~140,~~267~~675.4134 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 ~~169~~159 88100 ~~214~~263 1223 ~~483~~545 2223,~~934~~090,~~068~~093.4977 1011,~~954~~783,~~130~~064.2759 3037,~~961~~514,~~016~~665.5233 12,~~151~~218,~~934~~555.8699 6674,~~001~~606,~~150~~379.1468 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.~~451092~~466987% 0.~~023742~~000000% 0.000000% 0.~~474834~~466987% 0.~~411204~~415054% 0.~~015741~~000000% 0.000000% 0.~~426945~~415054% 30 Days 1.~~602564~~608510% 0.~~023742~~000000% 0.~~035613~~051887% 0.000000% 1.~~661918~~660397% 1.~~538389~~605008% 0.~~011643~~000000% 0.~~032872~~038025% 0.000000% 1.~~582904~~643033% 60 Days 0.~~237417~~285381% 0.~~059354~~064859% 0.~~569801~~635621% 0.000000% 0.~~866572~~985861% 0.~~224586~~366348% 0.~~040721~~036337% 0.~~546392~~588940% 0.000000% 0.~~811699~~991625% 90 Days 0.~~166192~~168634% 0.~~510446~~765339% 12.~~911206~~724089% 0.~~142450~~298353% 23.~~730294~~956415% 0.~~114303~~132832% 0.~~433088~~622393% 12.~~939324~~791727% 0.~~094292~~202176% 23.~~581007~~749128% 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 2.~~006173~~062524% 1.~~044634~~297185% 23.~~540361~~411597% 0.~~142450~~298353% 57.~~733618~~069659% 12.~~877279~~104188% 01.~~896655~~073784% 23.~~534328~~418691% 0.~~094292~~202176% 56.~~402555~~798839%

OTHER INFORMATION Current Period Class A Insufficient Funds 0.00 Principal Balance of Contaminated Properties 0.00 Periodic Advance ~~777~~819,~~251~~724.8307 Class A-1 524,901,347.20 35.85388172% ~~466~~430,~~681~~513,~~143~~774.9261 3839.~~21621745~~25101769% 6160.~~783774~~748973% 0.000000% Class A-2 175,794,347.20 12.00779873% 175,793,010.85 1416.~~39557611~~02748852% 23.~~820641~~223529% 0.000000% Class M-1 117,194,347.20 8.00507045% 117,193,010.85 910.~~59685996~~68477994% 45.~~798716~~342709% 0.000000% Class M-2 65,919,347.20 4.50268320% 65,918,010.85 56.~~39798333~~00990993% 4.~~198877~~674870% 0.000000% Class M-3 43,944,347.20 3.00166009% 43,943,010.85 34.~~59846478~~00639422% 12.~~799519~~003516% 0.000000% Class M-4 25,631,347.20 1.75077335% 25,630,010.85 2.~~09882503~~33675220% 1.~~499640~~669642% 0.000000% Class CE 0.00 0.00000000% 0.00 0.00000000% 01.~~899146~~001075% 0.000000% Class R-I 0.00 0.00000000% 0.00 0.00000000% 0.000000% 0.000000% Class R-II 0.00 0.00000000% 0.00 0.00000000% 0.000000% 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 8.~~073428~~058290% Weighted Average Net Coupon 7.~~573428~~558290% Weighted Average Pass-Through Rate 6.~~779344~~758834% Weighted Average Maturity(Stepdown Calculation ) ~~346~~344 Beginning Scheduled Collateral Loan Count 8,~~759~~061 Number Of Loans Paid In Full ~~335~~352 Ending Scheduled Collateral Loan Count 87,~~424~~709 Beginning Scheduled Collateral Balance 1,~~276~~157,~~229~~779,~~798~~624.6859 Ending Scheduled Collateral Balance 1,~~221~~096,~~159~~821,~~955~~942.3727 Ending Actual Collateral Balance at 30-~~Sep~~Nov-2003 1,~~221~~097,~~665~~339,~~510~~919.0860 Monthly P &I Constant 98,~~567~~675,~~636~~757.1314 Special Servicing Fee 0.00 Prepayment Penalties 1,~~128~~121,~~677~~299.4455 Realized Loss Amount 4088,~~742~~007.1274 Cumulative Realized Loss ~~133~~260,~~432~~103.5739 Ending Scheduled Balance for Premium Loans 1,~~221~~096,~~159~~821,~~955~~942.3727 Scheduled Principal ~~981~~900,~~344~~986.9685 Unscheduled Principal 5460,~~088~~056,~~498~~695.3547

Other Income 3763,~~054~~903.2964

Miscellaneous Reporting Net Monthly Excess Cashflow 4,~~864~~478,~~782~~696.3520 Extra Prinicpal Distribution Amount 4088,~~742~~007.1274 OC Amount 10,980,010.85 OC Deficiency Amount 4088,~~742~~007.1274 OC Release Amount 0.00 OC Target Amount 10,980,010.85 Stepdown NO Trigger Event NO Credit Enhancement Percentage 1416.~~395576~~027489%

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.~~646363~~614722 8.~~264549~~257224 7.~~620221~~586682 Weighted Average Net Rate 7.~~146363~~114722 7.~~764549~~757224 7.~~120221~~086681 Weighted Average Maturity ~~346~~344 ~~346~~344 ~~337~~335 Beginning Loan Count ~~743~~694 65,~~070~~562 1,~~359~~260 Loans Paid In Full 2023 ~~250~~249 4547 Ending Loan Count ~~723~~671 5,~~820~~313 1,~~314~~213 Beginning Scheduled Balance 9385,~~356~~923,~~316~~223.6007 ~~833~~751,~~100~~379,~~984~~675.3803 ~~189~~174,~~515~~382,~~563~~230.5609 Ending scheduled Balance 9082,~~146~~554,~~902~~779.8905 ~~793~~712,~~250~~625,~~369~~811.4107 ~~183~~166,~~742~~242,~~634~~605.6458 Record Date 0911/30/2003 0911/30/2003 0911/30/2003 Principal And Interest Constant ~~693~~638,~~295~~347.1529 65,~~304~~687,~~140~~702.6905 1,~~400~~286,~~496~~342.7416 Scheduled Principal 9893,~~431~~112.5871 ~~566~~517,~~470~~443.7526 ~~197~~183,~~037~~856.9579 Unscheduled Principal 3,~~110~~275,~~982~~331.1331 3938,~~284~~236,~~144~~420.2270 57,~~575~~955,~~890~~767.9772 Scheduled Interest ~~594~~545,~~863~~234.5758 5,~~737~~170,~~669~~258.9579 1,~~203~~102,~~458~~485.7937 Servicing Fees 3835,~~898~~801.4734 ~~347~~313,~~125~~074.3681 7872,~~964~~659.8428 Master Servicing Fees 0.00 0.00 0.00 Trustee Fee ~~233~~214.4883 21,~~083~~879.7203 ~~473~~436.8706 FRY Amount 0.00 0.00 0.00 Special Hazard Fee 0.00 0.00 0.00 Other Fee 7166,~~566~~488.0718 ~~519~~472,~~169~~345.6438 ~~143~~133,~~873~~403.6786 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 ~~555~~509,~~965~~433.1024 54,~~390~~857,~~544~~183.5898 1,~~124~~029,~~493~~826.9509 Realized Loss Amount 0.00 1296,~~738~~095.9741 ~~28,003~~(0.1503) Cumulative Realized Loss 0.00 93228,~~392~~305.2560 28,003.1512 Percentage of Cumulative Losses 0.000000 0.000238 0.000133 Prepayment Penalties 0.00 0.00 0.00 Special Servicing Fee 0.00 0.00 0.00 Pass-Through Rate 6.~~223453~~183151 76.~~013735~~999859 6.~~206222~~165671

Group Level Collateral Statement Group Group 4 Total Collateral Description Fixed 15/30 & ARM Mixed Fixed & Arm Weighted Average Coupon Rate 7.~~864612~~858954 8.~~073428~~058290 Weighted Average Net Rate 7.~~364613~~358954 7.~~573428~~558290 Weighted Average Maturity ~~337~~335 ~~346~~344 Beginning Loan Count ~~587~~545 8,~~759~~061 Loans Paid In Full 2033 ~~335~~352 Ending Loan Count ~~567~~512 87,~~424~~709 Beginning Scheduled Balance ~~160~~146,~~256~~094,~~934~~496.1440 1,~~276~~157,~~229~~779,~~798~~624.6859 Ending scheduled Balance ~~154~~135,~~020~~398,~~048~~746.4357 1,~~221~~096,~~159~~821,~~955~~942.3727 Record Date 0911/30/2003 0911/30/2003 Principal And Interest Constant 1,~~169~~063,~~703~~365.5564 98,~~567~~675,~~636~~757.1314 Scheduled Principal ~~119~~106,~~404~~574.6809 ~~981~~900,~~344~~986.9685 Unscheduled Principal 610,~~117~~589,~~481~~175.0374 5460,~~088~~056,~~498~~695.3547 Scheduled Interest 1956,~~050,298~~791.8755 87,~~586~~774,~~291~~770.1829 Servicing Fees 6660,~~773~~872.6265 ~~531~~482,~~762~~408.2908 Master Servicing Fees 0.00 0.00 Trustee Fee ~~400~~365.5315 32,~~191~~895.6007 FRY Amount 0.00 0.00 Special Hazard Fee 0.00 0.00 Other Fee ~~106~~96,~~727~~196.6702 ~~841~~768,~~337~~433.0544 Pool Insurance Fee 0.00 0.00 Spread Fee 1 0.00 0.00 Spread Fee 2 0.00 0.00 Spread Fee 3 0.00 0.00 Net Interest ~~983~~895,~~525~~918.2590 87,~~054~~292,~~528~~362.8821 Realized Loss Amount 0(8,087.0064) 4088,~~742~~007.1274 Cumulative Realized Loss 123,~~037~~794.1767 ~~133~~260,~~432~~103.5739 Percentage of Cumulative Losses 0.000021 0.000178 Prepayment Penalties 0.00 0.00 Special Servicing Fee 0.00 0.00 Pass-Through Rate 6.~~562440~~565814 6.~~779344~~758834

Filing Compare · MORTGAGE ASSET SECURITIZATION TRANSACTIONS INC SER 2003-OPT1