**SECURITIES AND EXCHANGE COMMISSION****Washington, D.C.  20549****UNITED STATES****FORM 10-K****[ X ] ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934****[    ] TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934**(State or Other Jurisdiction(Telephone number, including area code)**Lehman Mortgage Trust 2007-3****Delaware**(I.R.S. Employer Identification No.)**74-2440850**(Commission file number of Issuing Entity) (Address of Principal Executive Offices)**New York, New York****745 Seventh Avenue**(Zip Code)**10019****(212) 526-7000**Securities registered pursuant to Section 12(b) of the Act:**None.**Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. For the fiscal year ended December 31, 2007orFor the transition period from _____________ to _____________(Exact name of Issuing Entity)Securities registered pursuant to Section 12(g) of the Act:**None.**Indicate by check mark  if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.Indicate by check mark  if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K ( 229.405 of this chapter) is not contained herein, and will not be contained, to the best of registrant's knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.                      Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of "large accelerated filer", "accelerated filer", and "smaller reporting company" in Rule 12b-2 of the Exchange Act.Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act).**[ Yes]**Documents incorporated by reference:State the aggregate market value of the voting and non-voting common equity held by non-affiliates computed by reference to the price at which the common equity was last sold, or the average bid and asked price of such common equity, as of the last business day of the registrant's most recently completed second fiscal quarter.**Not Applicable.****[X No]****[ Yes] [X No]****[X Yes] [   N o ]****[X]****[  Yes] [X No]****Large accelerated filer [ ]****Accelerated filer [ ]****Non-accelerated filer [X]**(Exact Name of Registrant as Specified in its Charter)(Exact Name of Sponsor as Specified in its Charter)**Structured Asset Securities Corporation****Lehman Brothers Holdings Inc.****333-133985-59**Indicate by check mark whether the registrant has filed all documents and reports required to be filed by Section 12, 13 or 15(d) of the Securities Exchange Act of 1934 subsequent to the distribution of securities under a plan confirmed by a court.**Not Applicable.**Indicate the number of shares outstanding of each of the registrant's classes of common stock, as of the last practicable date.**Not Applicable.**List hereunder the following documents if incorporated by reference and the Part of the Form 10-K (e.g., Part I, Part II, etc.) into which the document is incorporated:  (1)Any annual report to security holders; (2) Any proxy or information statement; and (3)Any prospectus filed pursuant to Rule 424(b) or (c) under the Securities Act of 1933.  The listed documents should be clearly described for identification purposes (e.g., annual report to security holders for fiscal year ended December 24, 1980).**Not applicable.****Smaller reporting company [ ]****PART I****Item 1. Business.****Item 1A. Risk Factors.****Item 1B. Unresolved Staff Comments.****Item 2. Properties.****Item 3. Legal Proceedings.****Item 4. Submission of Matters to a Vote of Security Holders.**Not Applicable.Not Applicable.Not Applicable.None.Not Applicable.None.**Item 5. Market for Registrant's Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities.****Item 6. Selected Financial Data.****Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operation.****Item 7A. Quantitative and Qualitative Disclosures About Market  Risk.****Item 8. Financial Statements and Supplementary Data.****Item 9. Changes in and Disagreements With Accountants on Accounting and Financial Disclosure.****Item 9A. Controls and Procedures.****PART II**Not Applicable.Not Applicable.Not Applicable.Not Applicable.Not Applicable.Not Applicable.Not Applicable.Not Applicable.**Item 9A(T). Controls and Procedures.****Item 9B. Other Information.**None.**Item 10. Directors and Executive Officers and Corporate Governance.****Item 11. Executive Compensation.****Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters.****Item 13. Certain Relationships and Related Transactions, and Director Independence.****Item 14. Principal Accounting Fees and Services.****PART III**Not Applicable.Not Applicable.Not Applicable.Not Applicable.Not Applicable.**Item 1112(b) of Regulation AB.****Item 1117 of Regulation AB.****Item 1119 of Regulation AB.****Item 1122 of Regulation AB.****Significant Obligors of Pool Assets (Financial Information).****Legal Proceedings.****Affiliations and Certain Relationships and Related Transactions.****Compliance with Applicable Servicing Criteria**None.None.None.None.**Item 1115(b) of Regulation AB.**Information required by Item 1119 has been omitted from this annual report on Form 10-K because it is materially the same information as has been provided previously in a prospectus timely filed pursuant to Rule 424 promulgated under the Securities Act of 1933 under the same Central Index Key (CIK) code as this annual report on Form 10-k.Assurant:The asserting party did not have, during the Reporting Period, sufficient policies and procedures to capture for the information with respect to the Platform Transactions necessary to determine compliance with 1122(d)(4)(xii).LaSalle Bank National Association:LaSalle Bank National Association's ("LaSalle") Report on Assessment of Compliance with Servicing Criteria for 2007 (the "2007 Assessment") attached to this Report on Form 10-K describes in Appendix B the following material instance of noncompliance related to investor reporting:"1122(d)(3)(i)(A) and (B) - During the Reporting Period, certain monthly investor or remittance reports were not prepared in accordance with the terms set forth in the transaction agreements and certain investor reports did not provide the information calculated in accordance with the terms specified in the transaction agreements for which certain individual errors may or may not have been material."The investor reporting errors identified on LaSalle's 2007 Assessment as material instances of noncompliance (the "Investor Reporting Errors") included, for example, revised delinquency, REO, foreclosure, repurchase, payoff or modified loan counts, category indicators and/or balances.  The conclusion that the Investor Reporting Errors amounted to a material instance of noncompliance was based primarily on the aggregate number of errors as opposed to the materiality of any one error.The Investor Reporting Errors were generally caused by human error resulting primarily from high volume monthly data processing demands that had to be addressed within constricted time frames with less than a full complement of operational staff.  Between the fourth quarter of the Reporting Period and the date of the 2007 Assessment, LaSalle has employed additional operational staff to accommodate the high volume of monthly investor reporting requirements and minimize the risk of the Investor Reporting Errors recurring.  Other necessary controls are in place to minimize the risk of such errors.With respect to the specific pool assets and asset-backed securities related to the Investor Reporting Errors, the errors did not have, and are not reasonable likely in the future to have, any material impact or effect on pool asset performance, servicing of the pool assets and payments or expected payments on the mortgage-backed securities.In this transaction, LaSalle served as custodian.  Please note that this additional disclosure does not relate to LaSalle's custodial Servicing Criteria under Item 1122.Washington Mutual:Item 1122(d)(2)(vii)(D). Approximately 532 account reconciliation out of approximately 60,000 statements (or approximately .9% with reconciling items were not resolved within 90 days of their identification, due to the migration of functions to personnel in a separate geographic location. All such reconciling items have been resolved in the meantime and processes and procedures are in place to provide for on-going compliance with this requirement.Item 1122(d)(3)(i)(B) and (3)(ii).A programming change resulted in the miscalculation of some liquidation proceeds and the failure to include other liquidation proceeds, in the aggregate amount of approximately $9,694,614, in the September 2007 distribution with respect to 13 securitizations subject to Regulation AB.  The servicer in each of the securitizations remitted the applicable shortfall amount on October 1, 2007 to the applicable Trustee as required by the applicable pooling and servicing agreement.  The programming error was corrected in October 2007.Item 1122(d)(3)(ii).  Prepayment fees due to investors in 16 or more securitization subject to Reg AB were calculated incorrectly on certain loans with deferred interest, resulting in a shortfall in the distributions to those investors in an aggregate amount that is not expected to exceed $500,000.  The amounts due as the result of these miscalculations will be delivered to the applicable Trustee for distribution to the affected investors one analysis of the matter has been completed and the amounts due in the case of each securitization have been determined.  Processes and procedures **Item 1114(b)(2) of Regulation AB.****Credit Enhancement and Other Support, Except for Certain Derivatives Instruments (Information Regarding Significant Enhancement Providers Financial Information).****Certain Derivatives Instruments (Financial Information).****ADDITIONAL ITEMS PURSUANT TO GENERAL INSTRUCTION J**Reports on assesment of compliance with the servicing criteria for asset-backed securities are attached hereto under Item 15.**Servicer Compliance Statement.****Item 1123 of Regulation AB.**have been implemented and are currently being validated to provide for more accurate calculation of prepayment fees.Item 1122(d)(4)(vii).  With respect to 4 series of mortgage-backed securities, the servicer recently self-identified foreclosure cases initiated in connection with approximately 175 loans where the servicer did not expressly disclose the interests in the loans of the applicable trustees.  To the extent necessary under applicable law and court rules, the servicer will promptly move to amend those foreclosure pleadings.  Investors will be made whole if any direct losses or additional costs and expenses are incurred as a result of the failure to identify the interests of the trusts in the loans in any proceeding in which applicable law or court rules the trusts' interests must be disclosed.  The servicer will conduct further research and if additional loans are identified that were treated similarly, the servicer will make the applicable trusts whole if any losses arise from such treatment; andItem 1122(d)(4)(xiv).  Delinquent second lien mortgage loans were not charged off at 190 days as required by the applicable pooling and servicing agreements in the case of two securitizations subject to Reg AB.  All such mortgage loans were charged off as required upon identification of the non-compliance with this requirement.Servicer Compliance statements are attached hereto under Item 15.b) Exhibits identified in paragraph (a) above.**Item 15. Exhibits, Financial Statement Schedules.**c)  Not Applicable.**PART IV**a) ExhibitsTrust Agreement, dated as of March 1, 2007, among Structured Asset Securities Corporation, as Depositor, Aurora Loan Services LLC, as Master Servicer, and U.S. Bank National Association, as Trustee (incorporated herein by reference from Exhibit 4.1 of the Current Report on Form 8-K of the registrant, as filed with the Commission on April 13, 2007, Commission File Number 333-133985-59, CIK number 0001392866).Incorporated by reference as Exhibit 4.   Exhibit 4   Exhibit 10   Exhibit 33       Reports on assessment of compliance with servicing criteria for asset-backed securities.   Exhibit 34       Attestation reports on assessment of compliance with servicing criteria for asset-backed securities.    Exhibit 35       Servicer compliance statements.   Exhibit 31       Rule 13a-14(d)/15d-14(d) Certifications.a) Assurant Inc., as Sub-Contractor for Washington Mutual Bankb) Aurora Loan Services LLC, as Master Servicerc) Aurora Loan Services LLC, as Servicerd) Deutsche Bank National Trust Company, as Custodiane) IndyMac Bank, F.S.B., as Servicerf) LaSalle Bank National Association, as Custodiang) Newport Management Corporation, as Sub-Contractor for Aurora Loan Services LLCh) Newport Management Corporation, as Sub-Contractor for IndyMac Bank, F.S.B.i) U.S. Bank National Association, as Trustee, Paying Agent and Custodianj) Washington Mutual Bank, as Servicerk) Westlake Settlement Services, LLC, as Sub-Contractor for Aurora Loan Services LLCa) Assurant Inc., as Sub-Contractor for Washington Mutual Bankb) Aurora Loan Services LLC, as Master Servicerc) Aurora Loan Services LLC, as Servicerd) Deutsche Bank National Trust Company, as Custodiane) IndyMac Bank, F.S.B., as Servicerf) LaSalle Bank National Association, as Custodiang) Newport Management Corporation, as Sub-Contractor for Aurora Loan Services LLCh) Newport Management Corporation, as Sub-Contractor for IndyMac Bank, F.S.B.i) U.S. Bank National Association, as Trustee, Paying Agent and Custodianj) Washington Mutual Bank, as Servicerk) Westlake Settlement Services, LLC, as Sub-Contractor for Aurora Loan Services LLCa) Aurora Loan Services LLC, as Master Servicerb) Aurora Loan Services LLC, as Servicerc) IndyMac Bank, F.S.B., as Servicerd) Washington Mutual Bank, as Servicer**SIGNATURES****3/27/2008****/s/  E. Todd Whittemore****E. Todd WhittemoreExecutive Vice President, Master Servicing**Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.**Aurora Loan Services LLC, as Master Servicer****Lehman Mortgage Trust 2007-3****(Senior Officer in charge of the servicing function of Aurora Loan Services LLC, in its capacity as master servicer)****Title:**By (Signature and Title):**Name:**Date**EXHIBIT INDEX**EXHIBIT DESCRIPTIONTrust Agreement, dated as of March 1, 2007, among Structured Asset Securities Corporation, as Depositor, Aurora Loan Services LLC, as Master Servicer, and U.S. Bank National Association, as Trustee (incorporated herein by reference from Exhibit 4.1 of the Current Report on Form 8-K of the registrant, as filed with the Commission on April 13, 2007, Commission File Number 333-133985-59, CIK number 0001392866).      Exhibit 33       Reports on assessment of compliance with servicing criteria for asset-backed securities.      Exhibit 34       Attestation reports on assessment of compliance with servicing criteria for asset-backed securities.       Exhibit 35       Servicer compliance statement.      Exhibit 31       Rule 13a-14(d)/15d-14(d) Certifications.Incorporated by reference as Exhibit 4.     Exhibit 4      Exhibit 10a) Assurant Inc., as Sub-Contractor for Washington Mutual Bankb) Aurora Loan Services LLC, as Master Servicerc) Aurora Loan Services LLC, as Servicerd) Deutsche Bank National Trust Company, as Custodiane) IndyMac Bank, F.S.B., as Servicerf) LaSalle Bank National Association, as Custodiang) Newport Management Corporation, as Sub-Contractor for Aurora Loan Services LLCh) Newport Management Corporation, as Sub-Contractor for IndyMac Bank, F.S.B.i) U.S. Bank National Association, as Trustee, Paying Agent and Custodianj) Washington Mutual Bank, as Servicerk) Westlake Settlement Services, LLC, as Sub-Contractor for Aurora Loan Services LLCa) Assurant Inc., as Sub-Contractor for Washington Mutual Bankb) Aurora Loan Services LLC, as Master Servicerc) Aurora Loan Services LLC, as Servicerd) Deutsche Bank National Trust Company, as Custodiane) IndyMac Bank, F.S.B., as Servicerf) LaSalle Bank National Association, as Custodiang) Newport Management Corporation, as Sub-Contractor for Aurora Loan Services LLCh) Newport Management Corporation, as Sub-Contractor for IndyMac Bank, F.S.B.i) U.S. Bank National Association, as Trustee, Paying Agent and Custodianj) Washington Mutual Bank, as Servicerk) Westlake Settlement Services, LLC, as Sub-Contractor for Aurora Loan Services LLCa) Aurora Loan Services LLC, as Master Servicerb) Aurora Loan Services LLC, as Servicerc) IndyMac Bank, F.S.B., as Servicerd) Washington Mutual Bank, as Servicer