8-K 1 mab03op1.txt OCTOBER 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): October 27, 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 54-2102389 Pooling and Servicing Agreement) (Commission 54-2102390 (State or other File Number) IRS EIN jurisdiction 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 October 27, 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 October 27, 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: 10/31/03 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 October 27, 2003 distribution. EX-99.1

MASTR Asset Backed Securitizations Mortgage Pass-Through Certificates Record Date: 89/3130/03 Distribution Date: 910/2527/03 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.~~11000~~12000% ~~830~~797,~~375~~557,~~022~~872.8525 1,~~508~~502,~~745~~953.2850 3243,~~817~~079,~~150~~160.6081 A-2 57643LAJ5 SEN 1.~~53000~~54000% ~~312~~302,~~714~~878,~~140~~815.6858 ~~412~~414,~~000~~607.8845 911,~~835~~990,~~325~~682.1050 M-1 57643LAK2 MEZ 1.~~96000~~97000% 58,600,000.00 98102,~~903~~615.7811 0.00 M-2 57643LAL0 MEZ 2.~~96000~~97000% 51,275,000.00 ~~130~~135,~~694~~366.2800 0.00 M-3 57643LAM8 MEZ 3.~~86000~~87000% 21,975,000.00 7375,~~042~~594.4600 0.00 M-4 57643LAN6 MEZ 5.~~01000~~02000% 18,313,000.00 7981,~~005~~716.3368 0.00 MV-5 57643LAP1 MEZ 4.~~61000~~62000% 4,650,000.00 1819,~~459~~096.2100 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 54,~~051~~824,~~282~~040.9423 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 ~~847~~1,~~776~~128,677.7944 0.00 Totals 1,~~318~~276,~~882~~229,~~274~~798.3868 8,~~269~~334,~~910~~666.9541 4255,~~652~~069,~~475~~843.7031

Certificateholder Distribution Summary (continued) Current Ending Cumulative Realized Certificate Total Realized Class Loss Balance Distribution Losses A-1 0.00 ~~797~~754,~~557~~478,~~872~~711.2544 3444,~~325~~582,~~895~~114.8831 0.00 A-2 0.00 ~~302~~290,~~878~~888,~~815~~133.5807 1012,~~247~~405,~~325~~289.9895 0.00 M-1 0.00 58,600,000.00 98102,~~903~~615.7811 0.00 M-2 0.00 51,275,000.00 ~~130~~135,~~694~~366.2800 0.00 M-3 0.00 21,975,000.00 7375,~~042~~594.4600 0.00 M-4 0.00 18,313,000.00 7981,~~005~~716.3368 0.00 MV-5 0.00 4,650,000.00 1819,~~459~~096.2100 0.00 MF-5 0.00 10,000,000.00 50,000.00 0.00 CE 0.00 10,980,010.85 54,~~051~~824,~~282~~040.9423 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 ~~847~~1,~~776~~128,677.7944 0.00 Totals 0.00 1,~~276~~221,~~229~~159,~~798~~955.6836 5063,~~922~~404,~~386~~509.6572 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 ~~830~~797,~~375~~557,~~022~~872.8525 0.00 3243,~~817~~079,~~150~~160.6081 0.00 0.00 A-2 349,107,000.00 ~~312~~302,~~714~~878,~~140~~815.6858 0.00 911,~~835~~990,~~325~~682.1050 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,~~318~~276,~~882~~229,~~274~~798.3868 0.00 4255,~~652~~069,~~475~~843.7031 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 3243,~~817~~079,~~150~~160.6081 ~~797~~754,~~557~~478,~~872~~711.2544 0.~~84927896~~80340615 3243,~~817~~079,~~150~~160.6081 A-2 911,~~835~~990,~~325~~682.1050 ~~302~~290,~~878~~888,~~815~~133.5807 0.~~86758162~~83323489 911,~~835~~990,~~325~~682.1050 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 4255,~~652~~069,~~475~~843.7031 1,~~276~~221,~~229~~159,~~798~~955.6836 0.~~87174080~~83412483 4255,~~652~~069,~~475~~843.7031

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 ~~884~~849.~~22428160~~27896097 0.00000000 3445.~~94532063~~87281526 0.00000000 A-2 349,107,000.00 ~~895~~867.~~75442681~~58161704 0.00000000 2834.~~17280977~~34672608 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 3445.~~94532063~~87281526 ~~849~~803.~~27896097~~40614571 0.~~84927896~~80340615 3445.~~94532063~~87281526 A-2 0.00000000 2834.~~17280977~~34672608 ~~867~~833.~~58161704~~23489094 0.~~86758162~~83323489 2834.~~17280977~~34672608 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, ~~Bankrupcy~~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.~~11000~~12000% ~~830~~797,~~375~~557,~~022~~872.8525 1,~~508~~502,~~745~~953.2850 0.00 0.00 A-2 349,107,000.00 1.~~53000~~54000% ~~312~~302,~~714~~878,~~140~~815.6858 ~~412~~414,~~000~~607.8845 0.00 0.00 M-1 58,600,000.00 1.~~96000~~97000% 58,600,000.00 98102,~~903~~615.7811 0.00 0.00 M-2 51,275,000.00 2.~~96000~~97000% 51,275,000.00 ~~130~~135,~~694~~366.2800 0.00 0.00 M-3 21,975,000.00 3.~~86000~~87000% 21,975,000.00 7375,~~042~~594.4600 0.00 0.00 M-4 18,313,000.00 5.~~01000~~02000% 18,313,000.00 7981,~~005~~716.3368 0.00 0.00 MV-5 4,650,000.00 4.~~61000~~62000% 4,650,000.00 1819,~~459~~096.2100 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,~~370~~381,~~851~~948.2274 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,~~508~~502,~~745~~953.2850 0.00 ~~797~~754,~~557~~478,~~872~~711.2544 A-2 0.00 0.00 ~~412~~414,~~000~~607.8845 0.00 ~~302~~290,~~878~~888,~~815~~133.5807 M-1 0.00 0.00 98102,~~903~~615.7811 0.00 58,600,000.00 M-2 0.00 0.00 ~~130~~135,~~694~~366.2800 0.00 51,275,000.00 M-3 0.00 0.00 7375,~~042~~594.4600 0.00 21,975,000.00 M-4 0.00 0.00 7981,~~005~~716.3368 0.00 18,313,000.00 MV-5 0.00 0.00 1819,~~459~~096.2100 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 54,~~051~~824,~~282~~040.9423 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 ~~847~~1,~~776~~128,677.7944 0.00 100.00 Totals 0.00 0.00 8,~~269~~334,~~910~~666.9541 0.00 (4) Amount Does Not Include Excess Special Hazard, ~~Bankrupcy~~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.~~11000~~12000% ~~884~~849.~~22428160~~27896097 1.~~60658639~~60041902 0.00000000 0.00000000 A-2 349,107,000.00 1.~~53000~~54000% ~~895~~867.~~75442681~~58161704 1.~~18015646~~18762285 0.00000000 0.00000000 M-1 58,600,000.00 1.~~96000~~97000% 1000.00000000 1.~~68777782~~75111109 0.00000000 0.00000000 M-2 51,275,000.00 2.~~96000~~97000% 1000.00000000 2.~~54888893~~64000000 0.00000000 0.00000000 M-3 21,975,000.00 3.~~86000~~87000% 1000.00000000 3.~~32388896~~44000000 0.00000000 0.00000000 M-4 18,313,000.00 5.~~01000~~02000% 1000.00000000 4.~~31416644~~46222246 0.00000000 0.00000000 MV-5 4,650,000.00 4.~~61000~~62000% 1000.00000000 34.~~96972258~~10666667 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.~~60658639~~60041902 0.00000000 ~~849~~803.~~27896097~~40614571 A-2 0.00000000 0.00000000 1.~~18015646~~18762285 0.00000000 ~~867~~833.~~58161704~~23489094 M-1 0.00000000 0.00000000 1.~~68777782~~75111109 0.00000000 1000.00000000 M-2 0.00000000 0.00000000 2.~~54888893~~64000000 0.00000000 1000.00000000 M-3 0.00000000 0.00000000 3.~~32388896~~44000000 0.00000000 1000.00000000 M-4 0.00000000 0.00000000 4.~~31416644~~46222246 0.00000000 1000.00000000 MV-5 0.00000000 0.00000000 34.~~96972258~~10666667 0.00000000 1000.00000000 MF-5 0.00000000 0.00000000 5.00000000 0.00000000 1000.00000000 CE 0.00000000 0.00000000 ~~459~~439.~~98754506~~29402669 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 ~~8477767~~11286774.~~90000000~~40000000 0.00000000 1000.00000000 (6) Amount Does Not Include Excess Special Hazard, ~~Bankrupcy~~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 5163,~~528~~692,~~544~~865.2034 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) (3540,~~601~~742.4912) Prepayment Penalties ~~847~~1,~~776~~128,677.7944 Total Deposits 5264,~~340~~780,~~719~~800.5066 Withdrawals Reimbursement for Servicer Advances 0.00 Payment of Service Fee 1,~~418~~376,~~332~~290.8594 Payment of Interest and Principal 5063,~~922~~404,~~386~~509.6572 Total Withdrawals (Pool Distribution Amount) 5264,~~340~~780,~~719~~800.5066 Ending Balance 0.00

SERVICING FEES Gross Servicing Fee ~~549~~531,~~534~~762.8329 Radian ~~865~~841,~~499~~337.5105 Trustee Fee - Wells Fargo 3,~~298~~191.5160 Supported Prepayment/Curtailment Interest Shortfall 0.00 Net Servicing Fee 1,~~418~~376,~~332~~290.8594

OTHER ACCOUNTS Beginning Current Current Ending Account Type Balance Withdrawals Deposits Balance Reserve Fund 1,000.00 0.0100 0.0100 1,000.00 Reserve Fund 0.00 0.00 0.00 0.00

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 38 32 0 4140 45,~~550~~023,~~540~~536.9026 ~~521~~192,~~062~~308.2119 0.00 5,~~071~~215,~~603~~844.1145 30 Days ~~140~~135 12 53 0 ~~146~~140 1918,~~305~~793,~~862~~970.4232 65142,~~231~~241.9679 ~~919~~401,~~709~~579.7099 0.00 2019,~~290~~337,~~804~~792.0810 60 Days 2420 25 3648 0 6273 2,~~856~~743,~~961~~695.3761 ~~144~~497,~~489~~471.3915 46,~~673~~675,~~712~~079.5142 0.00 79,~~675~~916,~~163~~246.2718 90 Days 1314 3443 ~~154~~161 512 ~~206~~230 1,~~782~~396,~~410~~402.1156 45,~~203~~290,~~330~~881.0407 23,~~190~~692,~~717~~048.2592 ~~323~~1,~~375~~151,934.9486 2931,~~499~~531,~~833~~267.3441 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 ~~177~~169 7588 ~~198~~214 512 ~~455~~483 2322,~~945~~934,~~233~~068.9049 810,~~963~~954,~~592~~130.2927 2930,~~305~~961,~~201~~016.6752 ~~323~~1,~~375~~151,934.9486 6266,~~537~~001,~~403~~150.8014 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.~~433839~~451092% 0.~~034250~~023742% 0.000000% 0.~~468090~~474834% 0.~~356428~~411204% 0.~~040813~~015741% 0.000000% 0.~~397241~~426945% 30 Days 1.~~598356~~602564% 0.~~011417~~023742% 0.~~057084~~035613% 0.000000% 1.~~666857~~661918% 1.~~512162~~538389% 0.~~005109~~011643% 0.~~072038~~032872% 0.000000% 1.~~589309~~582904% 60 Days 0.~~274004~~237417% 0.~~022834~~059354% 0.~~411006~~569801% 0.000000% 0.~~707843~~866572% 0.~~223776~~224586% 0.~~011317~~040721% 0.~~366076~~546392% 0.000000% 0.~~601169~~811699% 90 Days 0.~~148419~~166192% 0.~~388172~~510446% 1.~~758192~~911206% 0.~~057084~~142450% 2.~~351867~~730294% 0.~~139610~~114303% 0.~~329232~~433088% 1.~~816449~~939324% 0.~~025329~~094292% 2.~~310621~~581007% 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.~~020779~~006173% 01.~~856262~~044634% 2.~~260532~~540361% 0.~~057084~~142450% 5.~~194657~~733618% 1.~~875548~~877279% 0.~~702087~~896655% 2.~~295376~~534328% 0.~~025329~~094292% 45.~~898340~~402555%

OTHER INFORMATION Current Period Class A Insufficient Funds 0.00 Principal Balance of Contaminated Properties 0.00 Periodic Advance ~~752~~777,~~365~~251.3083 Class A-1 524,901,347.20 35.85388172% ~~478~~466,~~671~~681,~~826~~143.4392 3738.~~50671132~~21621745% 6261.~~493281~~783774% 0.000000% Class A-2 175,794,347.20 12.00779873% 175,793,010.85 1314.~~77440105~~39557611% 23.~~732310~~820641% 0.000000% Class M-1 117,194,347.20 8.00507045% 117,193,010.85 9.~~18275149~~59685996% 4.~~591650~~798716% 0.000000% Class M-2 65,919,347.20 4.50268320% 65,918,010.85 5.~~16505812~~39798333% 4.~~017693~~198877% 0.000000% Class M-3 43,944,347.20 3.00166009% 43,943,010.85 3.~~44318953~~59846478% 1.~~721869~~799519% 0.000000% Class M-4 25,631,347.20 1.75077335% 25,630,010.85 2.~~00825987~~09882503% 1.~~434930~~499640% 0.000000% Class CE 0.00 0.00000000% 0.00 0.00000000% 0.~~860347~~899146% 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.~~075736~~073428% Weighted Average Net Coupon 7.~~575736~~573428% Weighted Average Pass-Through Rate 6.~~785250~~779344% Weighted Average Maturity(Stepdown Calculation ) ~~347~~346 Beginning Scheduled Collateral Loan Count 98,~~003~~759 Number Of Loans Paid In Full ~~244~~335 Ending Scheduled Collateral Loan Count 8,~~759~~424 Beginning Scheduled Collateral Balance 1,~~318~~276,~~882~~229,~~274~~798.3868 Ending Scheduled Collateral Balance 1,~~276~~221,~~229~~159,~~798~~955.6837 Ending Actual Collateral Balance at 3130-~~Aug~~Sep-2003 1,~~276~~221,~~706~~665,~~079~~510.6908 Monthly P &I Constant 9,~~890~~567,~~403~~636.2813 Special Servicing Fee 0.00 Prepayment Penalties ~~847~~1,~~776~~128,677.7944 Realized Loss Amount 3540,~~601~~742.4912 Cumulative Realized Loss 92133,~~690~~432.4557 Ending Scheduled Balance for Premium Loans 1,~~276~~221,~~229~~159,~~798~~955.6837 Scheduled Principal 1981,~~014,615~~344.7096 Unscheduled Principal 4154,~~637~~088,~~860~~498.0035

Other Income ~~279~~37,054.2229

Miscellaneous Reporting Net Monthly Excess Cashflow 54,~~086~~864,~~884~~782.4335 Extra Prinicpal Distribution Amount 3540,~~601~~742.4912 OC Amount 10,980,010.85 OC Deficiency Amount 3540,~~601~~742.4912 OC Release Amount 0.00 OC Target Amount 10,980,010.85 Stepdown NO Trigger Event NO Credit Enhancement Percentage 1314.~~774401~~395576%

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.~~664521~~646363 8.~~263659~~264549 7.~~623106~~620221 Weighted Average Net Rate 7.~~164521~~146363 7.~~763659~~764549 7.~~123106~~120221 Weighted Average Maturity ~~347~~346 ~~347~~346 ~~338~~337 Beginning Loan Count ~~761~~743 6,~~248~~070 1,~~390~~359 Loans Paid In Full 1820 ~~178~~250 3145 Ending Loan Count ~~743~~723 65,~~070~~820 1,~~359~~314 Beginning Scheduled Balance 9593,~~788~~356,~~514~~316.6360 ~~863~~833,~~494~~100,~~146~~984.3738 ~~194~~189,~~444~~515,~~712~~563.3456 Ending scheduled Balance 9390,~~356~~146,~~316~~902.6089 ~~833~~793,~~100~~250,~~984~~369.3841 ~~189~~183,~~515~~742,~~563~~634.5664 Record Date 0809/3130/2003 0809/3130/2003 0809/3130/2003 Principal And Interest Constant ~~712~~693,~~436~~295.5115 6,~~535~~304,~~601~~140.2869 1,~~437~~400,~~006~~496.3674 Scheduled Principal ~~100~~98,~~625~~431.5758 ~~589~~566,~~250~~470.0075 ~~201~~197,~~779~~037.1595 Unscheduled Principal 23,~~331~~110,~~572~~982.4613 2939,~~803~~284,~~911~~144.9922 45,~~727~~575,~~369~~890.6397 Scheduled Interest ~~611~~594,~~810~~863.9457 5,~~946~~737,~~351~~669.2895 1,~~235~~203,~~227~~458.2179 Servicing Fees 3938,~~911~~898.9347 ~~359~~347,~~789~~125.6536 8178,~~018~~964.6684 Master Servicing Fees 0.00 0.00 0.00 Trustee Fee ~~239~~233.6148 2,~~159~~083.8772 ~~486~~473.2387 FRY Amount 0.00 0.00 0.00 Special Hazard Fee 0.00 0.00 0.00 Other Fee 7371,~~000~~566.3907 ~~536~~519,~~330~~169.8964 ~~146~~143,~~799~~873.9167 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 ~~571~~555,~~899~~965.0110 5,~~586~~390,~~561~~544.6358 1,~~154~~124,~~208~~493.5595 Realized Loss Amount 0.00 3512,~~601~~738.4997 028,003.0015 Cumulative Realized Loss 0.00 8093,~~653~~392.2825 028,003.0015 Percentage of Cumulative Losses 0.00 0.00 0.00 Prepayment Penalties 0.00 0.00 0.00 Special Servicing Fee 0.00 0.00 0.00 Pass-Through Rate 6.~~247000~~223453 7.~~015317~~013735 6.~~214141~~206222

Group Level Collateral Statement Group Group 4 Total Collateral Description Fixed 15/30 & ARM Mixed Fixed & Arm Weighted Average Coupon Rate 7.~~864603~~864612 8.~~075736~~073428 Weighted Average Net Rate 7.~~364603~~364613 7.~~575736~~573428 Weighted Average Maturity ~~338~~337 ~~347~~346 Beginning Loan Count ~~604~~587 98,~~003~~759 Loans Paid In Full 1720 ~~244~~335 Ending Loan Count ~~587~~567 8,~~759~~424 Beginning Scheduled Balance ~~165~~160,~~154~~256,~~901~~934.0414 1,~~318~~276,~~882~~229,~~274~~798.3868 Ending scheduled Balance ~~160~~154,~~256~~020,~~934~~048.1443 1,~~276~~221,~~229~~159,~~798~~955.6837 Record Date 0809/3130/2003 0809/3130/2003 Principal And Interest Constant 1,~~205~~169,~~359~~703.1355 9,~~890~~567,~~403~~636.2813 Scheduled Principal ~~122~~119,~~960~~404.9868 1981,~~014,615~~344.7096 Unscheduled Principal 46,~~775~~117,~~005~~481.9203 4154,~~637~~088,~~860~~498.0035 Scheduled Interest 1,~~082~~050,~~398~~298.1587 8,~~875~~586,~~787~~291.5818 Servicing Fees 6866,~~814~~773.5962 ~~549~~531,~~534~~762.8329 Master Servicing Fees 0.00 0.00 Trustee Fee ~~412~~400.8053 3,~~298~~191.5160 FRY Amount 0.00 0.00 Special Hazard Fee 0.00 0.00 Other Fee ~~109~~106,~~368~~727.3267 ~~865~~841,~~499~~337.5105 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 1983,~~013,583~~525.5625 8,~~326~~054,~~252~~528.7588 Realized Loss Amount 0.00 3540,~~601~~742.4912 Cumulative Realized Loss 12,037.17 92133,~~690~~432.4557 Percentage of Cumulative Losses 0.00 0.00 Prepayment Penalties 0.00 0.00 Special Servicing Fee 0.00 0.00 Pass-Through Rate 6.~~566944~~562440 6.~~785250~~779344

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