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

                                    Form 13F

                               Form 13F COVER PAGE

Report for the Calendar Year or Quarter Ended: September 30, 2008

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           November 11, 2008
-------------------------------------   --------------------   -----------------
[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:               2
Form 13F Information Table Entry Total:        101
Form 13F Information Table Value Total: $1,146,846
                                        (thousands)

List of Other Included Managers:

No.   Form 13F File Number   Name
---   --------------------   ----
 2                           RSUI Indemnity Company
 3                           Alleghany Insurance Holdings LLC


SECURITIES AND EXCHANGE COMMISSIONS FORM 13F INFORMATION
PREPARED FOR ALLEGHANY CORPORATION
AS OF 09/30/08



          COLUMN 1              COLUMN 2     COLUMN 3  COLUMN 4       COLUMN 5          COLUMN 6    COLUMN 7    COLUMN 8
---------------------------- -------------- --------- --------- ------------------- --------------- -------- --------------
                                                                                       INVESTMENT                VOTING
                                                                                       DISCRETION               AUTHORITY
                                                        MARKET                      ---------------          --------------
                                                        VALUE     SHRS OR  SH/ PUT/ SOLE SHRD OTHER          SOLE SHRD NONE
       NAME OF ISSUER        TITLE OF CLASS   CUSIP    (X 1000)  PRIN AMT  PRN CALL  (A)  (B)  (C)   MANAGER  (A)  (B)  (C)
---------------------------- -------------- --------- --------- ---------- --- ---- ---- ---- ----- -------- ---- ---- ----
                                                                                
NABORS INDUSTRIES LTD        SHS            G6359F103    21,057    845,000 SH              X            2      X
NABORS INDUSTRIES LTD        SHS            G6359F103     3,988    160,000 SH              X            3      X
WEATHERFORD INTERNATIONAL LT COM            G95089101     3,817    151,840 SH              X            2      X
WEATHERFORD INTERNATIONAL LT COM            G95089101     4,525    180,000 SH              X            3      X
AT&T INC                     COM            00206R102     1,117     40,000 SH                   X       3      X
ABBOTT LABS                  COM            002824100       518      9,000 SH                   X       3      X
AGILENT TECHNOLOGIES INC     COM            00846U101       955     32,200 SH                   X       3      X
ALEXANDER & BALDWIN INC      COM            014482103       881     20,000 SH                   X       3      X
AMERICAN EXPRESS CO          COM            025816109     1,485     41,900 SH                   X       3      X
ANADARKO PETE CORP           COM            032511107    10,405    214,500 SH              X            2      X
ANADARKO PETE CORP           COM            032511107     3,202     66,000 SH              X            3      X
APACHE CORP                  COM            037411105    12,409    119,000 SH              X            2      X
APACHE CORP                  COM            037411105     4,849     46,500 SH              X            3      X
APPLIED MATLS INC            COM            038222105       757     50,000 SH                   X       3      X
AUTODESK INC                 COM            052769106     1,007     30,000 SH                   X       3      X
AUTOMATIC DATA PROCESSING IN COM            053015103       855     20,000 SH                   X       3      X
BAKER HUGHES INC             COM            057224107     5,146     85,000 SH                   X       2      X
BAKER HUGHES INC             COM            057224107     3,657     60,400 SH              X            3      X
BERKSHIRE HATHAWAY INC DEL   CL B           084670207     1,758        400 SH                   X       3      X
BOEING CO                    COM            097023105       860     15,000 SH                   X       3      X
BURLINGTON NORTHN SANTA FE C COM            12189T104   354,007  3,830,000 SH         X                 1      X
CABLEVISION SYS CORP         CL A NY CABLVS 12686C109       209      8,300 SH              X            3      X
CAMECO CORP                  COM            13321L108     1,740     78,000 SH              X            2      X
CAMECO CORP                  COM            13321L108     1,049     47,000 SH              X            3      X
CATERPILLAR INC DEL          COM            149123101       894     15,000 SH                   X       3      X
CHESAPEAKE ENERGY CORP       COM            165167101     1,793     50,000 SH              X            2      X
CHESAPEAKE ENERGY CORP       COM            165167101     6,276    175,000 SH              X            3      X
CHEVRON CORP NEW             COM            166764100    20,620    250,000 SH              X            2      X
CHEVRON CORP NEW             COM            166764100     4,479     54,300 SH              X            3      X
CHICAGO BRIDGE & IRON CO N V NY REGISTRY SH 167250109     9,235    480,000 SH              X            2      X
CHICAGO BRIDGE & IRON CO N V NY REGISTRY SH 167250109     3,656    190,000 SH              X            3      X
CHUBB CORP                   COM            171232101     1,647     30,000 SH                   X       3      X
COCA COLA CO                 COM            191216100     1,370     25,900 SH                   X       3      X
COMCAST CORP NEW             CL A           20030N101       665     33,900 SH              X            3      X
CONOCOPHILLIPS               COM            20825C104    23,440    320,000 SH              X            2      X
CONOCOPHILLIPS               COM            20825C104    29,945    408,800 SH              X            3      X
COSTCO WHSL CORP NEW         COM            22160K105     1,948     30,000 SH                   X       3      X
DARWIN PROFESSIONAL UNDERWRI COM            237502109   291,535  9,371,096 SH              X            3      X
DEERE & CO                   COM            244199105     1,485     30,000 SH                   X       3      X
DELL INC                     COM            24702R101       227     13,800 SH              X            3      X
DEVON ENERGY CORP NEW        COM            25179M103    36,708    402,500 SH              X            2      X
DEVON ENERGY CORP NEW        COM            25179M103    25,080    275,000 SH              X            3      X
DISNEY WALT CO               COM DISNEY     254687106     1,381     45,000 SH                   X       3      X
DOMTAR CORP                  COM            257559104     2,006    436,000 SH              X            2      X
DOMTAR CORP                  COM            257559104       754    164,000 SH              X            3      X
DU PONT EI DE NEMOURS & CO   COM            263534109     1,411     35,000 SH                   X       3      X
EOG RES INC                  COM            26875P101     5,636     63,000 SH              X            2      X
EOG RES INC                  COM            26875P101     9,572    107,000 SH              X            3      X
EXXON MOBIL CORP             COM            30231G102     2,330     30,000 SH                   X       3      X
FPL GROUP INC                COM            302571104     9,507    189,000 SH              X            2      X
FPL GROUP INC                COM            302571104     3,823     76,000 SH              X            3      X
FEDEX CORP                   COM            31428X106     1,186     15,000 SH                   X       3      X
FIDELITY NATL FINANCIAL      CL A           31620R105     3,584    243,800 SH              X            2      X
FIDELITY NATL FINANCIAL      CL A           31620R105       735     50,000 SH              X            3      X
FLOTEK INDS INC DEL          COM            343389102     2,530    230,000 SH              X            2      X
FLOTEK INDS INC DEL          COM            343389102     1,650    150,000 SH              X            3      X
GENERAL ELECTRIC CO          COM            369604103     1,775     69,600 SH                   X       3      X
GLAXOSMITHKLINE PLC          SPONSORED ADR  37733W105       300      6,900 SH              X            3      X
GLOBAL INDS LTD              COM            379336100    20,195  2,910,000 SH              X            2      X
GLOBAL INDS LTD              COM            379336100     7,565  1,090,000 SH              X            3      X
HOME DEPOT INC               COM            437076102       518     20,000 SH                   X       3      X
INTEL CORP                   COM            458140100     1,311     70,000 SH                   X       3      X
INTERNATIONAL BUSINESS MACHS COM            459200101     1,474     12,600 SH                   X       3      X
INTUIT                       COM            461202103       632     20,000 SH                   X       3      X
ISHARES INC                  MSCI JAPAN     464286848       988     92,700 SH              X            3      X



                                                                               1



SECURITIES AND EXCHANGE COMMISSIONS FORM 13F INFORMATION
PREPARED FOR ALLEGHANY CORPORATION
AS OF 09/30/08



          COLUMN 1              COLUMN 2     COLUMN 3  COLUMN 4       COLUMN 5          COLUMN 6    COLUMN 7    COLUMN 8
---------------------------- -------------- --------- --------- ------------------- --------------- -------- --------------
                                                                                       INVESTMENT                VOTING
                                                                                       DISCRETION               AUTHORITY
                                                        MARKET                      ---------------          --------------
                                                        VALUE     SHRS OR  SH/ PUT/ SOLE SHRD OTHER          SOLE SHRD NONE
       NAME OF ISSUER        TITLE OF CLASS   CUSIP    (X 1000)  PRIN AMT  PRN CALL  (A)  (B)  (C)   MANAGER  (A)  (B)  (C)
---------------------------- -------------- --------- --------- ---------- --- ---- ---- ---- ----- -------- ---- ---- ----
                                                                                
ISHARES TR                   S&P 500 INDEX  464287200       759      6,500 SH              X            3      X
JOHNSON AND JOHNSON          COM            478160104     1,787     25,800 SH                   X       3      X
KELLOGG CO                   COM            487836108     1,122     20,000 SH                   X       3      X
KEY ENERGY SVCS INC          COM            492914106     5,742    495,000 SH              X            2      X
KEY ENERGY SVCS INC          COM            492914106     2,378    205,000 SH              X            3      X
KOHLS CORP                   COM            500255104       387      8,400 SH              X            3      X
LAUDER ESTEE COS INC         CL A           518439104     1,248     25,000 SH                   X       3      X
LEGG MASON INC               COM            524901105       335      8,800 SH              X            3      X
LILLY ELI & CO               COM            532457108     1,541     35,000 SH                   X       3      X
LINCOLN NATIONAL CORP IND    COM            534187109       769     17,963 SH                   X       3      X
MANPOWER INC                 COM            56418H100       647     15,000 SH                   X       3      X
MARRIOTT INTL INC NEW        CL A           571903202       913     35,000 SH                   X       3      X
MCDERMOTT INTL INC           COM            580037109     4,344    170,000 SH              X            2      X
MCDERMOTT INTL INC           COM            580037109     2,427     95,000 SH              X            3      X
MEDTRONIC INC                COM            585055106     1,844     36,800 SH                   X       3      X
MICROSOFT CORP               COM            594918104     2,269     85,000 SH                   X       3      X
MILLIPORE CORP               COM            601073109     1,376     20,000 SH                   X       3      X
MOTOROLA INC                 COM            620076109       311     43,500 SH              X            3      X
NEWFIELD EXPL CO             COM            651290108       230      7,200 SH              X            3      X
NEWS CORP                    CL A           65248E104       839     70,000 SH                   X       3      X
NOBLE ENERGY INC             COM            655044105     1,668     30,000 SH                   X       3      X
NORDSTROM INC                COM            655664100       865     30,000 SH                   X       3      X
NOVARTIS AG                  SPONSORED ADR  66987V109     1,321     25,000 SH                   X       3      X
NUSTAR ENERGY LP             UNIT COM       67058H102     5,564    131,000 SH              X            2      X
NUSTAR ENERGY LP             UNIT COM       67058H102     2,505     59,000 SH              X            3      X
OLD REP INTL CORP            COM            680223104    21,038  1,650,000 SH              X            3      X
PETROLEO BRASILEIRO SA PETRO SPONSORED ADR  71654V408     7,846    178,500 SH              X            2      X
PETROLEO BRASILEIRO SA PETRO SPONSORED ADR  71654V408     3,142     71,500 SH              X            3      X
PFIZER INC                   COM            717081103    12,447    675,000 SH              X            2      X
PFIZER INC                   COM            717081103     5,993    325,000 SH              X            3      X
PLAINS EXPL& PRODTN CO       COM            726505100     2,408     68,500 SH              X            2      X
PLAINS EXPL& PRODTN CO       COM            726505100     1,108     31,500 SH              X            3      X
PROCTER & GAMBLE CO          COM            742718109     2,335     33,500 SH                   X       3      X
SPDR TR                      UNIT SER 1     78462F103       766      6,600 SH              X            3      X
SPDR GOLD TRUST              GOLD SHS       78463V107       587      6,900 SH              X            3      X
SANOFI AVENTIS               SPONSORED ADR  80105N105       214      6,500 SH              X            3      X
SCHLUMBERGER LTD             COM            806857108     1,952     25,000 SH                   X       3      X
SIEMENS A G                  SPONSORED ADR  826197501     1,174     12,500 SH                   X       3      X
SIGMA ALDRICH CORP           COM            826552101     1,048     20,000 SH                   X       3      X
SONY CORP                    ADR NEW        835699307       772     25,000 SH                   X       3      X
STATE STR CORP               COM            857477103       853     15,000 SH                   X       3      X
STATOILHYDRO ASA             SPONSORED ADR  85771P102     2,916    122,500 SH              X            2      X
STATOILHYDRO ASA             SPONSORED ADR  85771P102     1,011     42,500 SH              X            3      X
SYSCO CORP                   COM            871829107       925     30,000 SH                   X       3      X
TARGET CORP                  COM            87612E106       383      7,800 SH              X            3      X
TEXAS INSTRS INC             COM            882508104       495     23,000 SH                   X       3      X
3M CO                        COM            88579Y101     1,503     22,000 SH                   X       3      X
TIME WARNER INC              COM            887317105       468     35,700 SH              X            3      X
TIME WARNER CABLE            COM            88732J108       632     26,100 SH              X            3      X
TRICO MARINE SERVICES INC    COM NEW        896106200     5,337    312,500 SH              X            2      X
TRICO MARINE SERVICES INC    COM NEW        896106200     2,349    137,500 SH              X            3      X
US BANCORP DEL               COM NEW        902973304       245      6,800 SH              X            3      X
UNITEDHEALTH GROUP INC       COM            91324P102       239      9,400 SH              X            3      X
VALERO ENERGY CORP NEW       COM            91913Y100     5,151    170,000 SH              X            2      X
WAL MART STORES INC          COM            931142103     2,695     45,000 SH                   X       3      X
WASHINGTON POST CO           CL B           939640108       835      1,500 SH                   X       3      X
WELLS FARGO & CO NEW         COM            949746101     1,464     39,000 SH                   X       3      X
WEYERHAUSER CO               COM            962166104     1,212     20,000 SH                   X       3      X
WYETH                        COM            983024100     7,019    190,000 SH              X            2      X
WYETH                        COM            983024100     3,140     85,000 SH              X            3      X
XTO ENERGY INC               COM            98385X106     6,652    143,000 SH              X            2      X
XTO ENERGY INC               COM            98385X106     8,932    192,000 SH              X            3      X
ZENITH NATL INS CORP         COM            989390109     4,250    116,000 SH              X            3      X
GRAND TOTAL                                           1,146,846 31,059,199



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