UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    Form 13F

                               Form 13F COVER PAGE

Report for Calendar Year or Quarter Ended: March 31, 2011

Check here if Amendment [ ]; Amendment Number: __________

This Amendment (Check only one.): [ ] is a restatement.
                                  [ ] adds new holdings entries.

Institutional Investment Manager Filing this Report:

Name:    BB Biotech AG
Address: Vordergasse 3
         Schaffhausen Switzerland CH-8200

Form 13F File Number: 28-6964

The institutional investment manager filing this report and the person by whom
it is signed hereby represent that the person signing the report is authorized
to submit it, that all information contained herein is true, correct and
complete, and that it is understood that all required items, statements,
schedules, lists, and tables are considered integral parts of this form.

Person Signing this Report on Behalf of Reporting Manager:

Name:  Pascal Schmucki
Title: SIGNING AUTHORITY
Phone: 41 (44) 267 67 00


Signature, Place, and Date of Signing: /s/ Pascal Schmucki
                                       -----------------------------------------
                                       Schaffhausen, Switzerland, April 21, 2011

Report Type (Check only one.):

[X]  13F HOLDINGS REPORT. (Check here if all holdings of this reporting manager
     are reported in this report.)

[ ]  13F NOTICE. (Check here if no holdings reported are in this report, and
     all holdings are reported by other reporting manager(s).)

[ ]  13F COMBINATION REPORT. (Check here if a portion of the holdings for this
     reporting manager are reported in this report and a portion are reported by
     other reporting manager(s).)


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                              Form 13F SUMMARY PAGE

Report Summary:

Number of Other Included Managers:               3
Form 13F Information Table Entry Total:         17
Form 13F Information Table Value Total: $1,048,308
                                        (thousands)

List of Other Included Managers:

Provide a numbered list of the name(s) and Form 13F file number(s) of all
institutional investment managers with respect to which this report is filed,
other than the manager filing this report.



No.   Form 13F File Number   Name
---   --------------------   -------------------
                       
1     28-11193               Biotech Focus N.V.
2     28-11191               Biotech Invest N.V.
3     28-11189               Biotech Target N.V.



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                                  BB BIOTECH AG

                           FORM 13F INFORMATION TABLE



         COLUMN 1           COLUMN 2  COLUMN 3 COLUMN 4      COLUMN 5       COLUMN 6  COLUMN 7        COLUMN 8
--------------------------- -------- --------- -------- ------------------ ---------- -------- ----------------------
                              TITLE                                                               VOTING AUTHORITY
                               OF                VALUE    SHS OR  SH/ PUT/ INVESTMENT   OTHER  ----------------------
       NAME OF ISSUER         CLASS    CUSIP   (x$1000)  PRN AMT  PRN CALL DISCRETION MANAGERS    SOLE   SHARED NONE
--------------------------- -------- --------- -------- --------- --- ---- ---------- -------- --------- ------ -----
                                                                               
Affymetrix Inc              COM      00826T108   10,420 2,000,000 SH       DEFINED        1    2,000,000 NONE   NONE
Alexion Pharmaceuticals Inc COM      015351109   27,828   282,000 SH       DEFINED        2      282,000 NONE   NONE
Amgen Inc                   COM      031162100   26,725   500,000 SH       DEFINED        1      500,000 NONE   NONE
Amylin Pharmaceuticals Inc  COM      032346108   30,847 2,713,055 SH       DEFINED        2    2,713,055 NONE   NONE
Biomarin Pharmaceutical Inc COM      09061G101   24,190   962,583 SH       DEFINED        2      962,583 NONE   NONE
Celgene Corp                COM      151020104  260,932 4,532,039 SH       DEFINED        2    4,532,039 NONE   NONE
Dendreon Corp               COM      24823Q107   43,962 1,174,500 SH       DEFINED        2    1,174,500 NONE   NONE
Gilead Sciences Inc         COM      375558103  192,804 4,539,768 SH       DEFINED        1    4,539,768 NONE   NONE
Halozyme Therapeutics Inc   COM      40637H109   33,525 5,000,000 SH       DEFINED        3    5,000,000 NONE   NONE
Human Genome Sciences Inc   COM      444903108    5,382   196,056 SH       DEFINED        2      196,056 NONE   NONE
Idenix Pharmaceuticals Inc  COM      45166R204    6,976 2,101,308 SH       DEFINED        3    2,101,308 NONE   NONE
Immunogen Inc               COM      45253H101   35,598 3,924,778 SH       DEFINED        3    3,924,778 NONE   NONE
Incyte Corp                 COM      45337C102   70,770 4,465,000 SH       DEFINED        3    4,465,000 NONE   NONE
Isis Pharmaceuticals        COM      464330109   27,348 3,025,171 SH       DEFINED        3    3,025,171 NONE   NONE
Micromet Inc                COM      59509C105   37,449 6,681,397 SH       DEFINED        3    6,681,397 NONE   NONE
Optimer Pharmaceuticals Inc COM      68401H104   24,228 2,048,003 SH       DEFINED        3    2,048,003 NONE   NONE
Vertex Pharmaceuticals Inc  COM      92532F100  189,324 3,950,000 SH       DEFINED        3    3,950,000 NONE   NONE



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