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):  May 25, 2004


                    BEAR STEARNS ASSET BACKED SECURITIES TRUST
                 Asset-Backed Certificates, Series 2003-SD1 Trust
              (Exact name of registrant as specified in its charter)

New York (governing law of            333-91334-09        54-2126335
Pooling and Servicing Agreement)      (Commission         54-2126334
(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)


ITEM 5.  Other Events

 On May 25, 2004 a distribution was made to holders of BEAR STEARNS ASSET
 BACKED SECURITIES TRUST, Asset-Backed Certificates, Series 2003-SD1 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 Asset-Backed Certificates,
                                        Series 2003-SD1 Trust, relating to the
                                        May 25, 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.



                    BEAR STEARNS ASSET BACKED SECURITIES TRUST
                 Asset-Backed Certificates, Series 2003-SD1 Trust

              By:    Wells Fargo Bank, N.A. as Securities Administrator
              By:   /s/   Beth Belfield as Assistant Vice President
              By:    Beth Belfield as Assistant Vice President

              Date:  5/28/04
                                INDEX TO EXHIBITS


Exhibit Number            Description

EX-99.1                   Monthly report distributed to holders of Asset-
                          Backed Certificates, Series 2003-SD1 Trust,
                          relating to the May 25, 2004 distribution.





                   EX-99.1



Bear Stearns Asset Backed Securities
Asset-Backed Certificates



Record Date:             4/30/04
Distribution Date:       5/25/04


BSA  Series: 2003-SD1

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

<s>          <c>             <c>            <c>                <c>                <c>                <c>
A                07384YKL9       SEN         1.55000%                132,820,552.64         165,841.22       6,464,990.92
R-1              BSA03S1R1       RES         0.00000%                          0.00               0.00               0.00
R-2              BSA03S1R2       RES         0.00000%                          0.00               0.00               0.00
M-1              07384YKM7       MEZ         1.95000%                  8,295,000.00          13,030.06               0.00
M-2              07384YKN5       MEZ         3.15000%                  7,258,000.00          18,417.17               0.00
B                07384YKP0       SUB         4.60000%                  5,185,000.00          19,213.31               0.00
B-IO             BSA03SBIO       IO          0.00000%                          0.00         619,254.67               0.00
OC               BSA03S1OC       OC          0.00000%                  4,146,749.09               0.00               0.00
Totals                                                               157,705,301.73         835,756.43       6,464,990.92




                     Certificateholder Distribution Summary (continued)

                          Current             Ending                            Cumulative
                         Realized        Certificate              Total           Realized
Class                         Loss            Balance       Distribution             Losses

<s>            <c>               <c>                <c>                <c>
A                             0.00     126,355,561.72       6,630,832.14               0.00
R-1                           0.00               0.00               0.00               0.00
R-2                           0.00               0.00               0.00               0.00
M-1                           0.00       8,295,000.00          13,030.06               0.00
M-2                           0.00       7,258,000.00          18,417.17               0.00
B                             0.00       5,185,000.00          19,213.31               0.00
B-IO                          0.00               0.00         619,254.67               0.00
OC                            0.00       4,146,749.09               0.00               0.00
Totals                        0.00     151,240,310.81       7,300,747.35               0.00
<FN>
All distributions required by the Pooling and Servicing Agreement have been calculated by the
Certificate Administrator on behalf of the Trustee.




</FN>




                                                Principal Distribution Statement

                         Original            Beginning          Scheduled       Unscheduled
                             Face          Certificate          Principal         Principal                        Realized
Class                       Amount              Balance       Distribution      Distribution        Accretion       Loss (1)

<s>            <c>               <c>                  <c>                <c>               <c>              <c>
A                   186,599,000.00       132,820,552.64               0.00      6,464,990.92             0.00           0.00
R-1                          50.00                 0.00               0.00              0.00             0.00           0.00
R-2                          50.00                 0.00               0.00              0.00             0.00           0.00
M-1                   8,295,000.00         8,295,000.00               0.00              0.00             0.00           0.00
M-2                   7,258,000.00         7,258,000.00               0.00              0.00             0.00           0.00
B                     5,185,000.00         5,185,000.00               0.00              0.00             0.00           0.00
B-IO                          0.00                 0.00               0.00              0.00             0.00           0.00
OC                          454.31         4,146,749.09               0.00              0.00             0.00           0.00
Totals              207,337,554.31       157,705,301.73               0.00      6,464,990.92             0.00           0.00
<FN>
(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.

</FN>

 
 

                                               Principal Distribution Statement (continued)

                             Total               Ending           Ending               Total
                         Principal          Certificate      Certificate           Principal
 Class                    Reduction              Balance       Percentage        Distribution

 <s>            <c>               <c>                  <c>              <c>
 A                     6,464,990.92       126,355,561.72       0.67715026        6,464,990.92
 R-1                           0.00                 0.00       0.00000000                0.00
 R-2                           0.00                 0.00       0.00000000                0.00
 M-1                           0.00         8,295,000.00       1.00000000                0.00
 M-2                           0.00         7,258,000.00       1.00000000                0.00
 B                             0.00         5,185,000.00       1.00000000                0.00
 B-IO                          0.00                 0.00       0.00000000                0.00
 OC                            0.00         4,146,749.09   9,127.57608241                0.00

 Totals                6,464,990.92       151,240,310.81       0.72944003        6,464,990.92
 



                                     Principal Distribution Factors Statement

                             Original          Beginning         Scheduled        Unscheduled
                                 Face        Certificate         Principal          Principal
Class (2)                       Amount            Balance      Distribution       Distribution          Accretion


 <s>           <c>                   <c>                <c>               <c>                <c>
A                       186,599,000.00       711.79670116        0.00000000        34.64643926         0.00000000
R-1                              50.00         0.00000000        0.00000000         0.00000000         0.00000000
R-2                              50.00         0.00000000        0.00000000         0.00000000         0.00000000
M-1                       8,295,000.00      1000.00000000        0.00000000         0.00000000         0.00000000
M-2                       7,258,000.00      1000.00000000        0.00000000         0.00000000         0.00000000
B                         5,185,000.00      1000.00000000        0.00000000         0.00000000         0.00000000
B-IO                              0.00         0.00000000        0.00000000         0.00000000         0.00000000
OC                              454.31   9127576.08241069        0.00000000         0.00000000         0.00000000
<FN>
All classes are per $1,000 denomination.
</FN>







                                Principal Distribution Factors Statement (continued)

                                               Total             Ending            Ending              Total
                         Realized          Principal        Certificate       Certificate          Principal
Class                     Loss (3)          Reduction            Balance        Percentage       Distribution

<s>            <c>               <c>                <c>                <c>               <c>
A                       0.00000000        34.64643926       677.15026190        0.67715026        34.64643926
R-1                     0.00000000         0.00000000         0.00000000        0.00000000         0.00000000
R-2                     0.00000000         0.00000000         0.00000000        0.00000000         0.00000000
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
B                       0.00000000         0.00000000     1,000.00000000        1.00000000         0.00000000
B-IO                    0.00000000         0.00000000         0.00000000        0.00000000         0.00000000
OC                      0.00000000         0.00000000 9,127,576.08241069     9127.57608241         0.00000000
<FN>
(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.
</FN>









                                                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

<s>            <c>               <c>              <c>                <c>                <c>               <c>

A                   186,599,000.00         1.55000%     132,820,552.64         165,841.22              0.00               0.00
R-1                          50.00         0.00000%               0.00               0.00              0.00               0.00
R-2                          50.00         0.00000%               0.00               0.00              0.00               0.00
M-1                   8,295,000.00         1.95000%       8,295,000.00          13,030.06              0.00               0.00
M-2                   7,258,000.00         3.15000%       7,258,000.00          18,417.17              0.00               0.00
B                     5,185,000.00         4.60000%       5,185,000.00          19,213.31              0.00               0.00
B-IO                          0.00         0.00000%     157,705,301.73               0.00              0.00               0.00
OC                          454.31         0.00000%       4,146,749.09               0.00              0.00               0.00
Totals              207,337,554.31                                             216,501.76              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


 <s>            <c>               <c>                <c>                  <c>                 <c>
 A                             0.00               0.00           165,841.22              0.00        126,355,561.72
 R-1                           0.00               0.00                 0.00              0.00                  0.00
 R-2                           0.00               0.00                 0.00              0.00                  0.00
 M-1                           0.00               0.00            13,030.06              0.00          8,295,000.00
 M-2                           0.00               0.00            18,417.17              0.00          7,258,000.00
 B                             0.00               0.00            19,213.31              0.00          5,185,000.00
 B-IO                          0.00               0.00           619,254.67              0.00        151,240,310.81
 OC                            0.00               0.00                 0.00              0.00          4,146,749.09
 Totals                        0.00               0.00           835,756.43              0.00
 <FN>
 (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.


 </FN>
 




                                               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


<s>           <c>                  <c>              <c>                <c>               <c>                <c>
A                     186,599,000.00         1.55000%       711.79670116        0.88875728         0.00000000         0.00000000
R-1                            50.00         0.00000%         0.00000000        0.00000000         0.00000000         0.00000000
R-2                            50.00         0.00000%         0.00000000        0.00000000         0.00000000         0.00000000
M-1                     8,295,000.00         1.95000%      1000.00000000        1.57083303         0.00000000         0.00000000
M-2                     7,258,000.00         3.15000%      1000.00000000        2.53749931         0.00000000         0.00000000
B                       5,185,000.00         4.60000%      1000.00000000        3.70555641         0.00000000         0.00000000
B-IO                            0.00         0.00000%       760.62138534        0.00000000         0.00000000         0.00000000
OC                            454.31         0.00000%   9127576.08241069        0.00000000         0.00000000         0.00000000
<FN>

All classes are per $1,000 denomination.

</FN>




                                 Interest Distribution Factors Statement (continued)

                                                                                Remaining             Ending
                    Non-Supported                                 Total            Unpaid       Certificate/
                         Interest           Realized           Interest          Interest           Notional
Class                    Shortfall         Losses (6)       Distribution         Shortfall            Balance


<s>            <c>               <c>                <c>                <c>            <c>
A                       0.00000000         0.00000000         0.88875728        0.00000000       677.15026190
R-1                     0.00000000         0.00000000         0.00000000        0.00000000         0.00000000
R-2                     0.00000000         0.00000000         0.00000000        0.00000000         0.00000000
M-1                     0.00000000         0.00000000         1.57083303        0.00000000      1000.00000000
M-2                     0.00000000         0.00000000         2.53749931        0.00000000      1000.00000000
B                       0.00000000         0.00000000         3.70555641        0.00000000      1000.00000000
B-IO                    0.00000000         0.00000000         2.98669949        0.00000000       729.44037686
OC                      0.00000000         0.00000000         0.00000000        0.00000000   9127576.08241069
<FN>
(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.
</FN>











                                                  CERTIFICATEHOLDER ACCOUNT STATEMENT
                                                          CERTIFICATE ACCOUNT

<s>                                                                                      <c>
Beginning Balance                                                                                              0.00
Deposits
     Payments of Interest and Principal                                                                7,369,147.27
     Liquidations, Insurance Proceeds, Reserve Funds                                                           0.00
     Proceeds from Repurchased Loans                                                                           0.00
     Other Amounts (Servicer Advances)                                                                    93,940.42
     Realized Loss (Gains, Subsequent Expenses & Recoveries)                                                 904.40

     Prepayment Penalties                                                                                      0.00
Total Deposits                                                                                         7,463,992.09

Withdrawals
     Reimbursement for Servicer Advances                                                                 113,103.25
     Payment of Service Fee                                                                               50,141.49
     Payment of Interest and Principal                                                                 7,300,747.35
Total Withdrawals (Pool Distribution Amount)                                                           7,463,992.09


Ending Balance                                                                                                 0.00






                                                PREPAYMENT/CURTAILMENT INTEREST SHORTFALL
<s>                                                                                       <c>
Total Prepayment/Curtailment Interest Shortfall                                                                0.00

Servicing Fee Support                                                                                          0.00
Non-Supported Prepayment/Curtailment Interest Shortfall                                                        0.00








                                                             SERVICING FEES

<s>                                                                                       <c>
Gross Servicing Fee                                                                                       48,827.30
Master Servicing Fee                                                                                       1,314.19
Supported Prepayment/Curtailment Interest Shortfall                                                            0.00
Net Servicing Fee                                                                                         50,141.49







                                                             OTHER ACCOUNTS

                                                    Beginning            Current           Current            Ending
Account Type                                           Balance        Withdrawals          Deposits           Balance

<s>                                      <c>                 <c>                <c>               <c>
Financial Guaranty                                        0.00               0.00              0.00              0.00
Reserve Fund                                              0.00               0.00              0.00              0.00




                        LOAN STATUS STRATIFICATION/CREDIT ENHANCEMENT STATEMENT
                                                           DELINQUENCY STATUS

         DELINQUENT               BANKRUPTCY             FORECLOSURE             REO                     Total

<s>          <c>                    <c>                     <c>                     <c>                     <c>

          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                         22                     1                       0                       23
                                  2,351,817.59           78,173.22               0.00                    2,429,990.81

30 Days   33                      2                      2                       0                       37
          3,184,775.55            279,878.40             310,015.59              0.00                    3,774,669.54

60 Days   21                      3                      1                       0                       25
          2,365,230.19            308,676.12             118,252.07              0.00                    2,792,158.38

90 Days   12                      2                      1                       0                       15
          1,056,210.81            149,161.67             134,051.28              0.00                    1,339,423.76

120 Days  4                       3                      5                       0                       12
          309,849.30              292,638.46             355,114.31              0.00                    957,602.07

150 Days  1                       1                      5                       1                       8
          208,147.57              104,231.26             707,521.26              49,221.19               1,069,121.28

180+ Days 15                      6                      5                       4                       30
          1,711,381.86            523,464.46             467,853.88              328,669.10              3,031,369.30

Totals    86                      39                     20                      5                       150
          8,835,595.28            4,009,867.96           2,170,981.61            377,890.29              15,394,335.14


          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                         2.115385%              0.096154%               0.000000%               2.211538%
                                  1.552293%              0.051597%               0.000000%               1.603891%

30 Days   3.173077%               0.192308%              0.192308%               0.000000%               3.557692%
          2.102079%               0.184731%              0.204623%               0.000000%               2.491432%

60 Days   2.019231%               0.288462%              0.096154%               0.000000%               2.403846%
          1.561146%               0.203739%              0.078051%               0.000000%               1.842936%

90 Days   1.153846%               0.192308%              0.096154%               0.000000%               1.442308%
          0.697141%               0.098453%              0.088479%               0.000000%               0.884073%

120 Days  0.384615%               0.288462%              0.480769%               0.000000%               1.153846%
          0.204513%               0.193153%              0.234390%               0.000000%               0.632056%

150 Days  0.096154%               0.096154%              0.480769%               0.096154%               0.769231%
          0.137386%               0.068797%              0.466992%               0.032488%               0.705663%

180+ Days 1.442308%               0.576923%              0.480769%               0.384615%               2.884615%
          1.129580%               0.345507%              0.308802%               0.216935%               2.000825%

Totals    8.269231%               3.750000%              1.923077%               0.480769%              14.423077%
          5.831845%               2.646673%              1.432934%               0.249423%              10.160875%






                                                            OTHER INFORMATION

<s>                                                                                 <c>
Current Period Class A Insufficient Funds                                                                  0.00
Principal Balance of Contaminated Properties                                                               0.00

Periodic Advance                                                                                      93,940.42








 
 
                                   COLLATERAL STATEMENT
                                                                            
 Collateral Description                                                    Mixed Fixed

 Weighted Average Gross Coupon                                               6.734031%
 Weighted Average Net Coupon                                                 6.362497%
 Weighted Average Pass-Through Rate                                          6.352497%
 Weighted Average Maturity(Stepdown Calculation )                                  354
 Beginning Scheduled Collateral Loan Count                                       1,078

 Number Of Loans Paid In Full                                                       38
 Ending Scheduled Collateral Loan Count                                          1,040
 Beginning Scheduled Collateral Balance                                 157,705,301.73
 Ending Scheduled Collateral Balance                                    151,240,310.81
 Ending Actual Collateral Balance at 30-Apr-2004                        151,506,004.13
 Monthly P &I Constant                                                    1,152,174.92
 Special Servicing Fee                                                            0.00
 Prepayment Penalties                                                             0.00
 Realized Loss Amount                                                          (904.40)
 Cumulative Realized Loss                                                      (904.40)
 Ending Scheduled Balance for Premium Loans                             151,240,310.81
 Scheduled Principal                                                        267,181.32
 Unscheduled Principal                                                    6,197,809.60

 Required Overcollateralization Amount                                            0.00
 Overcollateralized Increase Amount                                               0.00
 Overcollateralized reduction Amount                                            904.40
 Specified O/C Amount                                                     4,146,749.09
 Overcollateralized Amount                                                4,146,749.09
 Overcollateralized Deficiency Amount                                             0.00
 Base Overcollateralized Amount                                                   0.00
 Extra principal distribution Amount                                              0.00
 Excess Cash Amount                                                         618,350.27
 
 
 
                                                       


 
   
   

               Miscellaneous Reporting
                                                           
   Three month rolling average                                      0.062132%
   Trigger Event                                                          YES
   Yield maintenance amount                                                 0