UNITED STATES


SECURITIES AND EXCHANGE
COMMISSION


Washington, D.C.
20549








FORM 10-K








[X] ANNUAL REPORT PURSUANT TO SECTION
13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934





For the
fiscal year ended December 31,
2007


or





[   ] TRANSITION REPORT
PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF
1934





For the
transition period from ________to _______





Commission
file number of issuing entity: 333-140436-17





MERRILL LYNCH MORTGAGE
INVESTORS TRUST, SERIES 2007-SD1


(Exact
name of issuing entity as specified in its charter)




Commission file number of depositor: 333-140436




Merrill Lynch Mortgage
Investors, Inc.


(Exact
name of registrant/depositor as specified in its charter)
  Merrill Lynch Mortgage
Lending, Inc.
 (Exact
name of sponsor as specified in its charter)


New
      York
            
            38-3768039
                38-3768038
                38-6850973
                38-6850972(State
      or other jurisdiction of
              incorporation
      or organization)
            
            (I.R.S.
      Employer
              Identification
      No.)





c/o
LaSalle Bank National Association
 135
South LaSalle Street, Chicago, Illinois 60603
 (Address of principal
executive offices)


312-904-7323
 (Registrant's
telephone number, including area code)


Securities
registered pursuant to Section 12(b) of the Act:




None.




Securities
registered pursuant to Section 12(g) 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.





oYes
            
            xNo





Indicate
by check mark if the registrant is not required to file pursuant to Section 13
or Section 15(d) of the Act.





oYes
            
            xNo





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.





xYes
            
            oNo





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.





x





Indicate
by check mark whether the registrant is a large accelerated filer, an
accelerated filer, a non- accelerated filer, or a small reporting
company.  See the definitions of “large accelerated filer,”
“accelerated filer” and “small reporting company” in Rule 12b-2 of the Exchange
Act.
 
 Large
      accelerated filer
              o
              Accelerated
      filer
              oNon-accelerated
      filer
              x
              (Do
      not check if a smaller reporting company)
              Smaller
      reporting company
              o




Indicate
by check mark whether the registrant is a shell company (as defined in Rule
12b-2 of the Act).   oYes  xNo




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.




DOCUMENTS INCORPORATED BY
REFERENCE




None.


PART I
  Item 1.
Business.
 Omitted.
 
 Item 1A. Risk
Factors.
 Omitted.
 
 Item 1B. Unresolved Staff
Comments.
 None.
  Item 2.
Properties.
 Omitted.
 
 Item 3. Legal Proceedings.
 Omitted.
 
 Item 4. Submission of Matters to a
Vote of Security Holders.
 Omitted.
 
 
 PART II
 
 Item 5. Market for Registrant’s
Common Equity, Related Stockholder Matters and Issuer Purchases of Equity
Securities.
 Omitted.
 
 Item 6. Selected Financial
Data.
 Omitted.
 
 Item 7. Management’s Discussion and
Analysis of Financial Condition and Results of Operations.
 Omitted.
 
 Item 7A. Quantitative and Qualitative
Disclosures About Market Risk.
 Omitted.
 
 Item 8. Financial Statements and
Supplementary Data.
 Omitted.
 
 Item 9. Changes in and Disagreements
With Accountants on Accounting and Financial Disclosure.
 Omitted.
 
 Item 9A. Controls and
Procedures.
 Omitted.
  Item 9A(T). Controls and
Procedures.
 Omitted.
 Item 9B. Other
Information.
 None.
 
 PART III
 
 Item 10. Directors, Executive
Officers and Corporate Governance.
 Omitted.
 
 Item 11. Executive
Compensation.
 Omitted.
 
 Item 12. Security Ownership of
Certain Beneficial Owners and Management and Related Stockholder
Matters.
 Omitted.
 
 Item 13. Certain Relationships and
Related Transactions, and Director Independence.
 Omitted.
 
 Item 14. Principal Accounting Fees
and Services.
 Omitted.
  ADDITIONAL DISCLOSURE ITEMS UNDER
REGULATION AB
  Item 1112(b) of Regulation AB.
Significant Obligors Financial Information.
 No single
obligor represents 10% or more of the pool assets held by the issuing
entity.
 
 Item
1114(b)2 of Regulation AB, Significant Enhancement Provider Financial
Information.
 No entity
or group of affiliated entities provides any external credit enhancement or
other support for the certificates within this transaction as described under
Item 1114(a) of Regulation AB.
 
 Item
1115(b) of Regulation AB, Certain Derivatives Instruments (Financial
Information).
 The
significance percentage of the derivative transaction entered into on behalf of
the issuing entity is less than 10%.
 Item 1117 of Regulation AB. Legal
Proceedings.
 The
registrant knows of no material pending legal proceedings involving the Trust
and all parties related to such Trust, other than routine litigation incidental
to the duties of those respective parties.
 
 Item 1119 of Regulation AB.
Affiliations and Certain Relationships and Related
Transactions.
 The
information regarding this Item has been previously filed in a 424(b)(5) filing
dated June 11, 2007.
 
 Item 1122 of Regulation AB.
Compliance with Applicable Servicing Criteria.
   The
following information regarding LaSalle Bank National Association's material
instances of noncompliance and related remedial action was provided by 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.
  Item 1123 of Regulation AB. Servicer
Compliance Statement.
 PART IV
 
  Item 15. Exhibits, Financial
Statement Schedules.
 
 (a) The
following is a list of documents filed as part of this Annual Report on Form
10-K:
 (1) Not
Applicable
 (2) Not
Applicable
 (3)


Exhibit
      Number
              Description4.1
              Pooling
      and Servicing Agreement (filed as an exhibit to Form 8-K on
      2007-06-26)10.1
              Mortgage
      Loan Sale and Assignment Agreement (filed as an exhibit to Form
      8-Kon
      2007-06-26)31
              Sarbanes-Oxley
      Certification33(a)
              Report
      on assessment of compliance with servicing criteria for asset-backed
      securities, Wilshire Credit Corporation, as Servicer33(b)
              Report
      on assessment of compliance with servicing criteria for asset-backed
      securities, LaSalle Bank National Association, as
  Trustee33(c)
              Report
      on assessment of compliance with servicing criteria for asset-backed
      securities, Land America Tax and Flood Services, as servicing function
      participant33(d)
              Report
      on assessment of compliance with servicing criteria for asset-backed
      securities, ZC Sterling Insurance Agency, Inc., as servicing function
      participant34(a)
              Attestation
      report on assessment of compliance with servicing criteria for
      asset-backed securities, Wilshire Credit Corporation, as
      Servicer34(b)
              Attestation
      report on assessment of compliance with servicing criteria for
      asset-backed securities, LaSalle Bank National Association, as
      Trustee34(c)
              Attestation
      report on assessment of compliance with servicing criteria for
      asset-backed securities, Land America Tax and Flood Services, as servicing
      function participant34(d)
              Attestation
      report on assessment of compliance with servicing criteria for
      asset-backed securities, ZC Sterling Insurance Agency, Inc., as servicing
      function participant35(a)
              Servicer
      compliance statement, Wilshire Credit Corporation, as
    Servicer35(b)
              Servicer
      compliance statement, LaSalle Bank National Association, as
      Trustee


(b) The
exhibits required to be filed by Registrant pursuant to Item 601 of Regulation
S-K:
 (31) Rule 13a-14(d)/15d-14(d) Certifications.
 (33)
Reports on assessment of compliance with servicing criteria for asset-backed
securities:
 Wilshire
      Credit Corporation, as ServicerLaSalle
      Bank National Association, as TrusteeLand America Tax and Flood Services, as servicing function
      participantZC Sterling Insurance Agency, Inc., as servicing function
      participant
 
 (34)
Attestation reports on assessment of compliance with servicing criteria for
asset-backed securities:
 Wilshire
      Credit Corporation, as ServicerLaSalle
      Bank National Association, as TrusteeLand America Tax and Flood Services, as servicing function
      participantZC Sterling Insurance Agency, Inc., as servicing function
      participant
  (35) Servicer Compliance Statements:
 Wilshire
      Credit Corporation, as ServicerLaSalle
      Bank National Association, as
Trustee
  (c) Not
Applicable.











SIGNATURES




Wilshire
      Credit Corporation, as ServicerMarch
      27, 2008
              /s/ Ken
      FryeBy: 
      Ken FryeTitle: 
      Senior Vice President, Loan ServicingSenior
      Officer in Charge of Securitization of theServicer





EXHIBIT INDEX




Exhibit
      Number
                Description4.1
                Pooling
      and Servicing Agreement (filed as an exhibit to Form 8-K on
      2007-06-26)10.1
                Mortgage
      Loan Sale and Assignment Agreement (filed as an exhibit to Form
      8-Kon
      2007-06-26)31
                Sarbanes-Oxley
      Certification33(a)
                Report
      on assessment of compliance with servicing criteria for asset-backed
      securities, Wilshire Credit Corporation, as Servicer33(b)
                Report
      on assessment of compliance with servicing criteria for asset-backed
      securities, LaSalle Bank National Association, as
  Trustee33(c)
                Report
      on assessment of compliance with servicing criteria for asset-backed
      securities, Land America Tax and Flood Services, as servicing function
      participant33(d)
                Report
      on assessment of compliance with servicing criteria for asset-backed
      securities, ZC Sterling Insurance Agency, Inc., as servicing function
      participant34(a)
                Attestation
      report on assessment of compliance with servicing criteria for
      asset-backed securities, Wilshire Credit Corporation, as
      Servicer34(b)
                Attestation
      report on assessment of compliance with servicing criteria for
      asset-backed securities, LaSalle Bank National Association, as
      Trustee34(c)
                Attestation
      report on assessment of compliance with servicing criteria for
      asset-backed securities, Land America Tax and Flood Services, as servicing
      function participant34(d)
                Attestation
      report on assessment of compliance with servicing criteria for
      asset-backed securities, ZC Sterling Insurance Agency, Inc., as servicing
      function participant35(a)
                Servicer
      compliance statement, Wilshire Credit Corporation, as
    Servicer35(b)
                Servicer
      compliance statement, LaSalle Bank National Association, as
      Trustee