**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, 2006


or





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





For
      the
      transition period from ________to _______





Commission
      file number of issuing entity: 333-129918-05




Credit
      Suisse Commercial Mortgage Trust 2006-C4


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




Commission
      file number of depositor: 333-129918




Credit
      Suisse First Boston Mortgage Securities Corp.


(Exact
      name of registrant as specified in its charter)




Delaware
            
            13-3320910(State
                or other jurisdiction of
              incorporation
                or organization)
            
            (I.R.S.
                Employer
              Identification
                No.)





11
        Madison Avenue, New York, New York 10010, (212) 325-2000
 (Address,
        including zip code, and telephone number, including area code, of registrant’s
        principal executive offices)





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
            
            x No





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


*The
          issuing entity has been required to file reports with respect to the period
          following the issuance of its securities and ending December 31, 2006.
 The
            issuing entity has filed a Form 15.


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


*The
          issuing entity has been required to file reports with respect to the period
          following the issuance of its securities and ending December 31, 2006.
 The
            issuing entity has filed a Form 15.


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.




Not
      applicable.





Indicate
      by check mark whether the registrant is a large accelerated filer, an
      accelerated filer, or a non-accelerated filer. See definition of “accelerated
      filer and large accelerated filer” in Rule 12b-2 of the Exchange Act (Check
      one):




Large
                accelerated filero
            Accelerated
                filero
            Non-accelerated
                filerx




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**




Pooling
        and Servicing Agreement (Filed as Exhibit 4.1 to the Registrant's Current
        Report
        on Form 8-K filed on October 13, 2006) incorporated by reference in Part
        IV.
 Mortgage
        Loan Purchase Agreement (Filed as Exhibit 10.1 to the Registrant’s Current
        Report on Form 8-K filed on October 13, 2006) incorporated by reference in
        Part
        IV.
 Mortgage
        Loan Purchase Agreement (Filed as Exhibit 10.2 to the Registrant’s Current
        Report on Form 8-K filed on October 13, 2006) incorporated by reference in
        Part
        IV.
 Mortgage
        Loan Purchase Agreement (Filed as Exhibit 10.3 to the Registrant’s Current
        Report on Form 8-K filed on October 13, 2006) incorporated by reference in
        Part
        IV.
 Mortgage
        Loan Purchase Agreement (Filed as Exhibit 10.4 to the Registrant’s Current
        Report on Form 8-K filed on October 13, 2006) incorporated by reference in
        Part
        IV.
 Mortgage
        Loan Purchase Agreement (Filed as Exhibit 10.5 to the Registrant’s Current
        Report on Form 8-K filed on October 13, 2006) incorporated by reference in
        Part
        IV.






**PART
      I**


**Item
      1B. Unresolved Staff Comments.**


None.










**PART
      II**







**Item
      9B. Other Information.**


None.







**Item
        1112(b) of Regulation AB. Significant Obligors Financial
        Information.**
 Credit
        Suisse (USA), Inc., as guarantor of leases of the property securing the 11
        Madison Avenue loan, constitutes a significant obligor within the meaning
        of
        1101(k)(3) of Regulation AB.  Selected financial data of Credit
        Suisse (USA), Inc. for the year ended December 31, 2006 is attached as
        Exhibit 99 to this Form 10-K and is deemed to be a part
        hereof.
  The
        11
        Madison Avenue loan constitutes a significant obligor within the meaning
        of
        1101(k)(2) of Regulation AB.  The net operating income for the most recent
        fiscal year is $13,558,747.09.
  **Item
        1114(b)(2) and 1115(b) of Regulation AB. Significant Enhancement Provider
        Financial Information.**
 No
        entity
        or group of affiliated entities provides any external credit enhancement
        or uses
        any derivative instruments or other support for the certificates within this
        transaction.
  **Item
        1117 of Regulation AB. Legal Proceedings.**
 The
        registrant knows of no material pending legal proceedings involving the Credit
        Suisse Commercial Mortgage Trust 2006-C4 (the "Trust") and all parties related
        to such Trust, other than routine litigation incidental to the duties of
        their
        respective parties.
  **Item
        1119 of Regulation AB. Affiliations and Certain Relationships and Related
        Transactions.**
 No
          additional affiliations, certain relationships or related transactions
          have been
          identified, other than those previoously disclosed in the prospectus filed
          on
          September 27, 2006.
  **Item
        1122 of Regulation AB. Compliance with Applicable Servicing
        Criteria.**
 The
          reports on assessment of compliance with servicing criteria for asset backed
          securities and related attestation reports are attached hereto under Item
          15.
 
 1122(d)(3)(i)
          - Delinquency Reporting - With respect to Wells Fargo Bank, N.A., as Trustee,
          the related report on assessment of compliance and attestation report state
          that
          during the reporting period, certain monthly investor or remittance reports
          included errors in the calculation and/or the reporting of delinquencies
          for the
          pool assets, which errors may or may not have been material. Wells Fargo
          Bank,
          N.A. has stated (1) that all such errors were the result of data processing
          errors and/or the mistaken interpretation of data provided by other parties
          participating in the servicing function; and (2) all necessary adjustments
          to
          data processing systems and/or interpretive clarifications have been made
          to
          correct those errors and to remedy related procedures.
 **Item
        1123 of Regulation AB. Servicer Compliance Statement.**
 The
        servicer compliance statements are attached hereto under Item 15.
 
 **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:


**Exhibit
                  Number**
              **Description**4.1
              Pooling
                  and Servicing Agreement (Filed as Exhibit 4.1 to the Registrant's
                  Current
                  Report on Form 8-K filed on October 13, 2006) (Incorporated by
                  reference)10.1
              Mortgage
                  Loan Purchase Agreement (Filed as Exhibit 10.1 to the Registrant’s Current
                  Report on Form 8-K filed on October 13, 2006) (Incorporated by
                  reference)10.2
              Mortgage
                  Loan Purchase Agreement (Filed as Exhibit 10.2 to the Registrant’s Current
                  Report on Form 8-K filed on October 13, 2006) (Incorporated by
                  reference)10.3
              Mortgage
                  Loan Purchase Agreement (Filed as Exhibit 10.3 to the Registrant’s Current
                  Report on Form 8-K filed on October 13, 2006) (Incorporated by
                  reference)10.4
              Mortgage
                  Loan Purchase Agreement (Filed as Exhibit 10.4 to the Registrant’s Current
                  Report on Form 8-K filed on October 13, 2006) (Incorporated by
                  reference)10.5
              Mortgage
                  Loan Purchase Agreement (Filed as Exhibit 10.5 to the Registrant’s Current
                  Report on Form 8-K filed on October 13, 2006) (Incorporated by
                  reference)31
              Rule
                  13a-14(d)/15(d)-14(d) Certifications33(a)
              Report
                  on assessment of compliance with servicing criteria for asset-backed
                  securities, Keycorp Real Estate Capital Markets, Inc., as Master
                  Servicer
                  No. 133(b)
              Report
                  on assessment of compliance with servicing criteria for asset-backed
                  securities, NCB, FSB, as Master Servicer No. 233(c)
              Report
                  on assessment of compliance with servicing criteria for asset-backed
                  securities, LNR Partners, Inc., as Special Servicer No.
                  133(d)
              Report
                  on assessment of compliance with servicing criteria for asset-backed
                  securities, National Consumer Cooperative Bank, as Special Servicer
                  No. 233(e)
              Report
                  on assessment of compliance with servicing criteria for asset-backed
                  securities, LaSalle Bank National Association, as Certificate
                  Administrator and Paying Agent33(f)
              Report
                  on assessment of compliance with servicing criteria for asset-backed
                  securities, Wells Fargo Bank, N.A., as Trustee34(a)
              Attestation
                  report on assessment of compliance with servicing criteria for
                  asset-backed securities, Keycorp Real Estate Capital Markets, Inc.,
                  as
                  Master Servicer No. 134(b)
              Attestation
                  report on assessment of compliance with servicing criteria for
                  asset-backed securities, NCB, FSB, as Master Servicer No.
                  234(c)
              Attestation
                  report on assessment of compliance with servicing criteria for
                  asset-backed securities, LNR Partners, Inc., as Special Servicer
                  No.
                  134(d)
              Attestation
                  report on assessment of compliance with servicing criteria for
                  asset-backed securities, National Consumer Cooperative Bank, as
                  Special
                  Servicer No. 234(e)
              Attestation
                  report on assessment of compliance with servicing criteria for
                  asset-backed securities,  LaSalle Bank National Association, as
                  Certificate Administrator and Paying Agent34(f)
              Attestation
                  report on assessment of compliance with servicing criteria for
                  asset-backed securities, Wells Fargo Bank, N.A., as
                  Trustee35(a)
              Servicer
                  compliance statement, Keycorp Real Estate Capital Markets, Inc.,
                  as Master
                  Servicer No. 135(b)
              Servicer
                  compliance statement, NCB, FSB, as Master Servicer No.
                  235(c)
              Servicer
                  compliance statement, LNR Partners, Inc., as Special Servicer No.
                  135(d)
              Servicer
                  compliance statement, National Consumer Cooperative Bank, as Special
                  Servicer No. 235(e)
              Servicer
                  compliance statement, LaSalle Bank National Association, as Certificate
                  Administrator and Paying Agent35(f)
              Servicer
                  compliance statement, Wells Fargo Bank, N.A., as
                  Trustee99
              Selected financial
                  data of Credit Suisse (USA), Inc. for the year ended December 31,
                  2006




(b)
      The
      exhibits required to be filed by Registrant pursuant to Item 601 of Regulation
      S-K are listed above and in the Exhibit Index that immediately follows the
      signature page hereof.




(c)
      Not
      Applicable.








**SIGNATURES**





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.




Credit
              Suisse First Boston Mortgage Securities Corp.March
              29, 2007
            /s/
              Jeffrey AltabefBy: Jeffrey
              AltabefTitle: Vice
              President





**EXHIBIT
      INDEX**


**Exhibit
                        Number**
                    **Description**4.1
                    Pooling
                        and Servicing Agreement (Filed as Exhibit 4.1 to the Registrant's
                        Current
                        Report on Form 8-K filed on October 13, 2006) (Incorporated
                        by
                        reference)10.1
                    Mortgage
                        Loan Purchase Agreement (Filed as Exhibit 10.1 to the Registrant’s Current
                        Report on Form 8-K filed on October 13, 2006) (Incorporated
                        by
                        reference)10.2
                    Mortgage
                        Loan Purchase Agreement (Filed as Exhibit 10.2 to the Registrant’s Current
                        Report on Form 8-K filed on October 13, 2006) (Incorporated
                        by
                        reference)10.3
                    Mortgage
                        Loan Purchase Agreement (Filed as Exhibit 10.3 to the Registrant’s Current
                        Report on Form 8-K filed on October 13, 2006) (Incorporated
                        by
                        reference)10.4
                    Mortgage
                        Loan Purchase Agreement (Filed as Exhibit 10.4 to the Registrant’s Current
                        Report on Form 8-K filed on October 13, 2006) (Incorporated
                        by
                        reference)10.5
                    Mortgage
                        Loan Purchase Agreement (Filed as Exhibit 10.5 to the Registrant’s Current
                        Report on Form 8-K filed on October 13, 2006) (Incorporated
                        by
                        reference)31
                    Rule
                        13a-14(d)/15(d)-14(d) Certifications33(a)
                    Report
                        on assessment of compliance with servicing criteria for asset-backed
                        securities, Keycorp Real Estate Capital Markets, Inc., as
                        Master Servicer
                        No. 133(b)
                    Report
                        on assessment of compliance with servicing criteria for asset-backed
                        securities, NCB, FSB, as Master Servicer No. 233(c)
                    Report
                        on assessment of compliance with servicing criteria for asset-backed
                        securities, LNR Partners, Inc., as Special Servicer No.
                        133(d)
                    Report
                        on assessment of compliance with servicing criteria for asset-backed
                        securities, National Consumer Cooperative Bank, as Special Servicer
                        No. 233(e)
                    Report
                        on assessment of compliance with servicing criteria for asset-backed
                        securities, LaSalle Bank National Association, as Certificate
                        Administrator and Paying Agent33(f)
                    Report
                        on assessment of compliance with servicing criteria for asset-backed
                        securities, Wells Fargo Bank, N.A., as Trustee34(a)
                    Attestation
                        report on assessment of compliance with servicing criteria
                        for
                        asset-backed securities, Keycorp Real Estate Capital Markets,
                        Inc., as
                        Master Servicer No. 134(b)
                    Attestation
                        report on assessment of compliance with servicing criteria
                        for
                        asset-backed securities, NCB, FSB, as Master Servicer No.
                        234(c)
                    Attestation
                        report on assessment of compliance with servicing criteria
                        for
                        asset-backed securities, LNR Partners, Inc., as Special Servicer
                        No.
                        134(d)
                    Attestation
                        report on assessment of compliance with servicing criteria
                        for
                        asset-backed securities, National Consumer Cooperative Bank,
                        as Special
                        Servicer No. 234(e)
                    Attestation
                        report on assessment of compliance with servicing criteria
                        for
                        asset-backed securities,  LaSalle Bank National Association, as
                        Certificate Administrator and Paying Agent34(f)
                    Attestation
                        report on assessment of compliance with servicing criteria
                        for
                        asset-backed securities, Wells Fargo Bank, N.A., as
                        Trustee35(a)
                    Servicer
                        compliance statement, Keycorp Real Estate Capital Markets,
                        Inc., as Master
                        Servicer No. 135(b)
                    Servicer
                        compliance statement, NCB, FSB, as Master Servicer No.
                        235(c)
                    Servicer
                        compliance statement, LNR Partners, Inc., as Special Servicer
                        No.
                        135(d)
                    Servicer
                        compliance statement, National Consumer Cooperative Bank,
                        as Special
                        Servicer No. 235(e)
                    Servicer
                        compliance statement, LaSalle Bank National Association,
                        as Certificate
                        Administrator and Paying Agent35(f)
                    Servicer
                        compliance statement, Wells Fargo Bank, N.A., as
                        Trustee99
                    Selected
                        financial data of Credit Suisse (USA), Inc. for year ended December
                        31, 2006.