UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549

                                  SCHEDULE 13G

                    Under the Securities Exchange Act of 1934

                                (Amendment No. )*

                              SANGAMO BIOSCIENCES
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                                (Name of Issuer)

                                     Common
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                         (Title of Class of Securities)

                                    80067710
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                                 (CUSIP Number)

                               December 28, 2007
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             (Date of Event Which Requires Filing of this Statement)

     Check the appropriate box to designate the rule pursuant to which this
Schedule is filed:

           |X|  Rule 13d-1(b)
 
           |_|  Rule 13d-1(c)

           |_|  Rule 13d-1(d)

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*    The remainder of this cover page shall be filled out for a reporting
     person's initial filing on this form with respect to the subject class of
     securities, and for any subsequent amendment containing information which
     would alter the disclosures provided in a prior cover page.

     The information required in the remainder of this cover page shall not be
deemed to be "filed" for the purpose of Section 18 of the Securities Exchange
Act of 1934 or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).

<PAGE>

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1. NAME OF REPORTING PERSONS
   I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)

William Blair & Company, L.L.C.
36-2214610
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2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

                                                                        (a)  |_|
                                                                        (b)  |_|
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3. SEC USE ONLY


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4. CITIZENSHIP OR PLACE OF ORGANIZATION

222 W Adams
Chicago, IL 60606
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  NUMBER OF    5.   SOLE VOTING POWER

   SHARES           3437261
               -----------------------------------------------------------------
BENEFICIALLY   6.   SHARED VOTING POWER

  OWNED BY          -0-
               -----------------------------------------------------------------
    EACH       7.   SOLE DISPOSITIVE POWER

  REPORTING         3437261
               -----------------------------------------------------------------
   PERSON      8.   SHARED DISPOSITIVE POWER

    WITH            -0-
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9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

3437261
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10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*

                                                                          |-|
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11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

8.56
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12. TYPE OF REPORTING PERSON*

BD, IA
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                      *SEE INSTRUCTIONS BEFORE FILLING OUT!

<PAGE>

Item 1(a). Name of Issuer:
SANGAMO BIOSCIENCES

Item 1(b). Address of Issuer's Principal Executive Offices:
501 Canal Blvd Ste A100
Richmond, CA 94804-3559

Item 2(a). Name of Person Filing:
William Blair & Company, L.L.C.

Item 2(b). Address of Principal Business Office, or if None, Residence:
222 W Adams
Chicago, IL 60606

Item 2(c). Citizenship:
U.S.A.

Item 2(d). Title of Class of Securities:
Common

Item 2(e). CUSIP Number:
80067710

Item 3.    If This Statement is Filed Pursuant to Rule 13d-1(b), or 13d-2(b)
           or (c), Check Whether the Person Filing is a:

      (a)  |X| Broker or dealer registered under Section 15 of the Exchange Act.

      (b)  |_| Bank as defined in Section 3(a)(6) of the Exchange Act.

      (c)  |_| Insurance company as defined in Section 3(a)(19) of the Exchange
               Act.

      (d)  |_| Investment company registered under Section 8 of the Investment 
               Company Act.

      (e)  |X| An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E);

      (f)  |_| An employee benefit plan or endowment fund in accordance with
               Rule 13d-1(b)(1)(ii)(F);

      (g)  |_| A parent holding company or control person in accordance with
               Rule 13d-1(b)(1)(ii)(G);

      (h)  |_| A savings association as defined in Section 3(b) of the Federal 
               Deposit Insurance Act;

      (i)  |_| A church plan that is excluded from the definition of an 
               investment company under Section 3(c)(14) of the Investment
               Company Act;

      (j)  |_| Group, in accordance with Rule 13d-1(b)(1)(ii)(J).

<PAGE>

Item 4.    Ownership.

     Provide the following information regarding the aggregate number and
percentage of the class of securities of the issuer identified in Item 1.

     (a)   Amount beneficially owned: 
             3437261

     (b)   Percent of class: 
             8.56

     (c)   Number of shares as to which such person has:

           (i)   Sole power to vote or to direct the vote 
                   3437261

           (ii)  Shared power to vote or to direct the vote 
                   -0-

           (iii) Sole power to dispose or to direct the disposition of
                   3437261

           (iv)  Shared power to dispose or to direct the disposition of 
                   -0-

Item 5.    Ownership of Five Percent or Less of a Class.

     If this statement is being filed to report the fact that as of the date
hereof the reporting person has ceased to be the beneficial owner of more than
five percent of the class of securities check the following [].

Item 6.    Ownership of More Than Five Percent on Behalf of Another Person.

Item 7.    Identification and Classification of the Subsidiary Which Acquired
           the Security Being Reported on by the Parent Holding Company or 
           Control Person.

Item 8.    Identification and Classification of Members of the Group.

Item 9.    Notice of Dissolution of Group.

Item 10.   Certifications.

           By signing below I certify that, to the best of my knowledge and
           belief, the securities referred to above were acquired and are held
           in the ordinary course of business and were not acquired and not held
           for the purpose of or with the effect of changing or influencing the
           control of the issuer of the securities and were not acquired and are
           not held in connection with or as a participant in any transaction
           having such purpose or effect.

<PAGE>

                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

                                    January 9, 2008
                                    ------------------------------------------
                                                     (Date)


                                    /s/ Michelle Seitz
                                    ------------------------------------------
                                                   (Signature)


                                    Principal & Manager of Investment Services
                                    ------------------------------------------
                                                  (Name/Title)


The original statement shall be signed by each person on whose behalf the
statement is filed or his authorized representative. If the statement is signed
on behalf of a person by his authorized representative other than an executive
officer or general partner of the filing person, evidence of the
representative's authority to sign on behalf of such person shall be filed with
the statement, provided, however, that a power of attorney for this purpose
which is already on file with the Commission may be incorporated by reference.
The name and any title of each person who signs the statement shall be typed or
printed beneath his signature.

NOTE: Schedules filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See 240.13d-7 for other parties
for whom copies are to be sent.

Attention: Intentional misstatements or omissions of fact constitute Federal
criminal violations (See 18 U.S.C. 1001)