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

                                    Form 13F

                               Form 13F COVER PAGE

Report for the Calendar Year or Quarter Ended: December 31, 2006

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:    Alleghany Corporation
Address: 7 Times Square Tower, 17th Floor
         New York, NY  10036

Form 13F File Number:  28-1590

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:    Peter R. Sismondo
Title:   Vice President
Phone:   212-752-1356

Signature, Place, and Date of Signing:

    /s/ Peter R. Sismondo          New York, NY             February 12, 2007
--------------------------------------------------------------------------------
          [Signature]              [City, State]                 [Date]



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).)



                              Form 13F SUMMARY PAGE


                                         
Report Summary:
Number of Other Included Managers:                   3
Form 13F Information Table Entry Total:             68
Form 13F Information Table Value Total:     $1,092,658
                                            (thousands)


List of Other Included Managers:
      No.   Form 13F File Number                       Name

      2                                       RSUI Indemnity Company
      3                                       Capitol Indemnity Corporation
      4                                       Alleghany Insurance Holdings LLC

SECURITIES AND EXCHANGE COMMISSIONS FORM 13F INFORMATION
PREPARED FOR ALLEGHANY CORPORATION
AS OF 12/31/06




COLUMN 1           COLUMN 2      COLUMN 3      COLUMN 4         COLUMN 5            COLUMN 6      COLUMN 7           COLUMN 8
------------------------------------------------------------------------------------------------------------------------------------
                                                                                    INVESTMENT
                                                MARKET                              DISCRETION                   VOTING AUTHORITY
NAME OF            TITLE OF                     VALUE      SHRS OR    SH/   PUT/ SOLE SHRD OTHER               SOLE    SHRD    NONE
 ISSUER             CLASS          CUSIP       (x$1000)    PRN AMT    PRN   CALL (A)  (B)   (C)    MANAGER     (A)     (B)     (C)
------------------------------------------------------------------------------------------------------------------------------------
                                                                                        
AT&T INC           COM           00206R102       1,788         50,000  SH                     X        4        X
AGILENT TECHNO-
 LOGIES INC        COM           00846U101         697         20,000  SH                     X        4        X
ALEXANDER &
 BALDWIN INC       COM           014482103         887         20,000  SH                     X        4        X
AMERICAN EXPRESS
 CO                COM           025816109       1,517         25,000  SH                     X        4        X
AMERICAN INTL
 GROUP INC         COM           026874107       1,433         20,000  SH                     X        4        X
AMERIPRISE FINL
 INC               COM           03076C106         273          5,000  SH                     X        4        X
ANADARKO PETE CORP COM           032511107      32,640        750,000  SH               X              2        X
ANADARKO PETE CORP COM           032511107      10,880        250,000  SH               X              3        X
APACHE CORP        COM           037411105      32,424        487,500  SH               X              2        X
APACHE CORP        COM           037411105      10,808        162,500  SH               X              3        X
APPLERA CORP       COM AP BIO
                    GRP          038080103       1,835         50,000  SH                     X        4        X
APPLIED MATLS INC  COM           038222105         923         50,000  SH                     X        4        X
AUTODESK INC       COM           052769106       1,214         30,000  SH                     X        4        X
BELO CORP          COM SER A     080555105         919         50,000  SH                     X        4        X
BERKSHIRE HATHAWAY
 INC DEL           CL B          084670207       1,466            400  SH                     X        4        X
BERKSHIRE HATHAWAY
 INC DEL           CL B          084670207       4,147          1,131  SH               X              3        X
BOEING CO          COM           097023105       1,333         15,000  SH                     X        4        X
BURLINGTON NORTHN
 SANTA FE C        COM           12189T104     428,786      5,809,319  SH         X                    1        X
CATERPILLAR INC
 DEL               COM           149123101       1,840         30,000  SH                     X        4        X
CHEVRON CORP NEW   COM           166764100       1,471         20,000  SH               X              1        X
CHEVRON CORP NEW   COM           166764100      30,515        415,000  SH               X              2        X
CHEVRON CORP NEW   COM           166764100      11,397        155,000  SH               X              3        X
CHEVRON CORP NEW   COM           166764100       8,088        110,000  SH               X              4        X
CHUBB CORP         COM           171232101       1,587         30,000  SH                     X        4        X
CIMAREX ENERGY CO  COM           171798101      10,950        300,000  SH               X              2        X
CIMAREX ENERGY CO  COM           171798101       7,300        200,000  SH               X              3        X
COCA COLA CO       COM           191216100       1,206         25,000  SH                     X        4        X
CONOCOPHILLIPS     COM           20825C104       1,439         20,000  SH               X              1        X
CONOCOPHILLIPS     COM           20825C104      23,024        320,000  SH               X              2        X
CONOCOPHILLIPS     COM           20825C104      12,951        180,000  SH               X              3        X
CONOCOPHILLIPS     COM           20825C104      36,695        510,000  SH               X              4        X
COSTCO WHSL CORP
 NEW               COM           22160K105       1,586         30,000  SH                     X        4        X
DTE ENERGY CO      COM           233331107       5,810        120,000  SH               X              2        X
DTE ENERGY CO      COM           233331107       1,936         40,000  SH               X              3        X




COLUMN 1           COLUMN 2      COLUMN 3      COLUMN 4         COLUMN 5            COLUMN 6      COLUMN 7           COLUMN 8
------------------------------------------------------------------------------------------------------------------------------------
                                                                                    INVESTMENT
                                                MARKET                              DISCRETION                   VOTING AUTHORITY
NAME OF            TITLE OF                     VALUE      SHRS OR    SH/   PUT/ SOLE SHRD OTHER               SOLE    SHRD    NONE
 ISSUER             CLASS          CUSIP       (x$1000)    PRN AMT    PRN   CALL (A)  (B)   (C)    MANAGER     (A)     (B)     (C)
------------------------------------------------------------------------------------------------------------------------------------
                                                                                        
DARWIN
 PROFESSIONAL
  UNDERWRI         COM           237502109     219,752          9,371  SH              X               4        X
DEERE & CO         COM           244199105       1,426         15,000  SH                     X        4        X
DEVON ENERGY CORP
 NEW               COM           25179M103      37,732        562,500  SH               X              2        X
DEVON ENERGY CORP
 NEW               COM           25179M103      12,578        187,500  SH               X              3        X
DISNEY WALT CO     COM DISNEY    254687106       1,542         45,000  SH                     X        4        X
DOMINION RES INC
 VA NEW            COM           25746U109      11,318        135,000  SH               X              2        X
DOMINION RES INC
 VA NEW            COM           25746U109       5,450         65,000  SH               X              3        X
DOW CHEM CO        COM           260543103         798         20,000  SH                     X        4        X
DU PONT EI DE
 NEMOURS & CO      COM           263534109       1,461         30,000  SH                     X        4        X
EXXON MOBIL CORP   COM           30231G102       2,299         30,000  SH                     X        4        X
FEDEX CORP         COM           31428X106       1,629         15,000  SH                     X        4        X
FIFTH THIRD BANCOP COM           316773100         819         20,000  SH                     X        4        X
GENERAL ELECTRIC
 CO                COM           369604103       1,674         45,000  SH                     X        4        X
GREAT PLAINS
 ENERGY INC        COM           391164100       3,180        100,000  SH               X              2        X
GREAT PLAINS
 ENERGY INC        COM           391164100       1,908         60,000  SH               X              3        X
HSBC HLDGS PLC     SPON ADR NEW  404280406      18,330        200,000  SH               X              2        X
HSBC HLDGS PLC     SPON ADR NEW  404280406       9,165        100,000  SH               X              3        X
HOME DEPOT INC     COM           437076102         402         10,000  SH                     X        4        X
IDEARC INC         COM           451663108         430         15,000  SH               X              2        X
IDEARC INC         COM           451663108         286         10,000  SH               X              3        X
INTEL CORP         COM           458140100       1,418         70,000  SH                     X        4        X
INTERNATIONAL
 BUSINESS MACHS    COM           459200101       1,166         12,000  SH                     X        4        X
INTUIT             COM           461202103         610         20,000  SH                     X        4        X
LAUDER ESTEE COS
 INC               CL A          518439104       1,021         25,000  SH                     X        4        X
LIBERTY MEDIA HLDG
 CORP              CAP COM SER A 53071M302         539          5,500  SH                     X        4        X
LILLY ELI & CO     COM           532457108       1,563         30,000  SH                     X        4        X
LINCOLN NATIONAL
 CORP IND          COM           534187109       1,193         17,963  SH                     X        4        X
MAGNA INTL INC     CL A          559222401       5,369         66,650  SH               X              2        X
MAGNA INTL INC     CL A          559222401       2,686         33,350  SH               X              3        X
MANPOWER INC       COM           56418H100       1,499         20,000  SH                     X        4        X
MCCLATCHY CO       COM           579489105       1,299         30,000  SH                     X        4        X
MEDTRONIC INC      COM           585055106       1,605         30,000  SH                     X        4        X
MICROSOFT CORP     COM           594918104       2,090         70,000  SH                     X        4        X
MILLIPORE CORP     COM           601073109       1,332         20,000  SH                     X        4        X
NEWS CORP          CL A          65248E104       1,504         70,000  SH                     X        4        X
NOBLE ENERGY INC   COM           655044105       1,472         30,000  SH                     X        4        X
NORDSTROM INC      COM           655664100       1,974         40,000  SH                     X        4        X
NOVARTIS AG        SPONSORED ADR 66987V109       1,436         25,000  SH                     X        4        X
PFIZER INC         COM           717081103       3,367        130,000  SH               X              2        X
PFIZER INC         COM           717081103       1,813         70,000  SH               X              3        X




COLUMN 1           COLUMN 2      COLUMN 3      COLUMN 4         COLUMN 5            COLUMN 6      COLUMN 7           COLUMN 8
------------------------------------------------------------------------------------------------------------------------------------
                                                                                    INVESTMENT
                                                MARKET                              DISCRETION                   VOTING AUTHORITY
NAME OF            TITLE OF                     VALUE      SHRS OR    SH/   PUT/ SOLE SHRD OTHER               SOLE    SHRD    NONE
 ISSUER             CLASS          CUSIP       (x$1000)    PRN AMT    PRN   CALL (A)  (B)   (C)    MANAGER     (A)     (B)     (C)
------------------------------------------------------------------------------------------------------------------------------------
                                                                                        
PROCTER & GAMBLE
 CO                COM           742718109       1,928         30,000  SH                     X        4        X
SCHLUMBERGER LTD   COM           806857108       2,526         40,000  SH                     X        4        X
SIGMA ALDRICH CORP COM           826552101       1,166         15,000  SH                     X        4        X
SONY CORP          ADR NEW       835699307       1,071         25,000  SH                     X        4        X
STATE STR CORP     COM           857477103       1,012         15,000  SH                     X        4        X
TEXAS INSTRS INC   COM           882508104         576         20,000  SH                     X        4        X
3M CO              COM           88579Y101       1,714         22,000  SH                     X        4        X
VERIZON COMMUNI-
 CATIONS           COM           92343V104      11,172        300,000  SH               X              2        X
VERIZON COMMUNI-
 CATIONS           COM           92343V104       7,448        200,000  SH               X              3        X
WACHOVIA CORP
 2ND NEW           COM           929903102       1,139         20,000  SH                     X        4        X
WAL MART STORES
 INC               COM           931142103       1,847         40,000  SH                     X        4        X
WASHINGTON POST CO CL B          939640108         746          1,000  SH                     X        4        X
WEYERHAUSER CO     COM           962166104       1,413         20,000  SH                     X        4        X

GRAND TOTAL                                  1,092,658     13,538,684