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

                                    Form 13F

                               Form 13F COVER PAGE

Report for the Calendar Year or Quarter Ended: March 31, 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           May 14, 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:           80
Form 13F Information Table Value Total:   $1,232,881
                                          (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 03/31/08



          COLUMN 1              COLUMN 2     COLUMN 3  COLUMN 4       COLUMN 5             COLUMN 6       COLUMN 7    COLUMN 8
       --------------        -------------- --------- --------- ------------------- --------------------- -------- --------------
                                                                                          INVESTMENT                   VOTING
                                                        MARKET                            DISCRETION                  AUTHORITY
                                                        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     5,403    160,000 SH                 X              1       X
NABORS INDUSTRIES LTD        SHS            G6359F103    28,536    845,000 SH                 X              2       X
WEATHERFORD INTERNATIONAL LT COM            G95089101     6,522     90,000 SH                 X              1       X
WEATHERFORD INTERNATIONAL LT COM            G95089101     5,502     75,920 SH                 X              2       X
AT&T INC                     COM            00206R102     1,532     40,000 SH                         X      3       X
AGILENT TECHNOLOGIES INC     COM            00846U101       895     30,000 SH                         X      3       X
ALEXANDER & BALDWIN INC      COM            014482103       862     20,000 SH                         X      3       X
AMERICAN EXPRESS CO          COM            025816109     1,530     35,000 SH                         X      3       X
AMERICAN INTL GROUP INC      COM            026874107       865     20,000 SH                         X      3       X
APACHE CORP                  COM            037411105     4,350     36,000 SH                 X              1       X
APACHE CORP                  COM            037411105    19,814    164,000 SH                 X              2       X
APPLERA CORP                 COM AP BIO GRP 038080103     1,643     50,000 SH                         X      3       X
APPLIED MATLS INC            COM            038222105       976     50,000 SH                         X      3       X
AUTODESK INC                 COM            052769106       944     30,000 SH                         X      3       X
AUTOMATIC DATA PROCESSING IN COM            053015103       848     20,000 SH                         X      3       X
BERKSHIRE HATHAWAY INC DEL   CL B           084670207     1,789        400 SH                         X      3       X
BOEING CO                    COM            097023105     1,116     15,000 SH                         X      3       X
BURLINGTON NORTHN SANTA FE C COM            12189T104   368,880  4,000,000 SH         X                      1       X
CATERPILLAR INC DEL          COM            149123101     1,957     25,000 SH                         X      3       X
CHESAPEAKE ENERGY CORP       COM            165167101     8,076    175,000 SH                 X              1       X
CHESAPEAKE ENERGY CORP       COM            165167101     2,308     50,000 SH                 X              2       X
CHEVRON CORP NEW             COM            166764100    10,243    120,000 SH                 X              1       X
CHEVRON CORP NEW             COM            166764100    29,876    350,000 SH                 X              2       X
CHEVRON CORP NEW             COM            166764100     9,390    110,000 SH                 X              3       X
CHUBB CORP                   COM            171232101     1,484     30,000 SH                         X      3       X
COCA COLA CO                 COM            191216100     1,522     25,000 SH                         X      3       X
CONOCOPHILLIPS               COM            20825C104    12,575    165,000 SH                 X              1       X
CONOCOPHILLIPS               COM            20825C104    24,387    320,000 SH                 X              2       X
CONOCOPHILLIPS               COM            20825C104    38,867    510,000 SH                         X      3       X
COSTCO WHSL CORP NEW         COM            22160K105     1,949     30,000 SH                         X      3       X
DARWIN PROFESSIONAL UNDERWRI COM            237502109   210,756  9,371,096 SH                         X      3       X
DEERE & CO                   COM            244199105     2,413     30,000 SH                         X      3       X
DEVON ENERGY CORP NEW        COM            25179M103    17,006    163,000 SH                 X              1       X
DEVON ENERGY CORP NEW        COM            25179M103    50,548    484,500 SH                 X              2       X
DISNEY WALT CO               COM DISNEY     254687106     1,412     45,000 SH                         X      3       X
DOMTAR CORP                  COM            257559104     1,120    164,000 SH                 X              1       X
DOMTAR CORP                  COM            257559104     2,978    436,000 SH                 X              2       X
DOW CHEM CO                  COM            260543103       737     20,000 SH                         X      3       X
DU PONT EI DE NEMOURS & CO   COM            263534109     1,403     30,000 SH                         X      3       X
EXXON MOBIL CORP             COM            30231G102     2,537     30,000 SH                         X      3       X
FEDEX CORP                   COM            31428X106     1,390     15,000 SH                         X      3       X
FPL GROUP INC                COM            302571104       176      2,802 SH                 X              1       X
FIDELITY NATL FINANCIAL      CL A           31620R105       917     50,000 SH                 X              1       X
FIDELITY NATL FINANCIAL      CL A           31620R105     4,468    243,800 SH                 X              2       X
GENERAL ELECTRIC CO          COM            369604103     6,847    185,000 SH                 X              1       X
GENERAL ELECTRIC CO          COM            369604103    15,359    415,000 SH                 X              2       X
GENERAL ELECTRIC CO          COM            369604103     1,665     45,000 SH                         X      3       X
GOLDMAN SACHS GROUP INC      COM            38141G104     3,424     20,700 SH                 X              1       X
GOLDMAN SACHS GROUP INC      COM            38141G104     7,161     43,300 SH                 X              2       X
HSBC HLDGS PLC               SPON ADR NEW   404280406     8,230    100,000 SH                 X              1       X
HSBC HLDGS PLC               SPON ADR NEW   404280406    16,460    200,000 SH                 X              2       X
HOME DEPOT INC               COM            437076102       559     20,000 SH                         X      3       X
INTEL CORP                   COM            458140100     1,483     70,000 SH                         X      3       X
INTERNATIONAL BUSINESS MACHS COM            459200101     1,382     12,000 SH                         X      3       X
INTL PAPER CO                COM            460146103     4,760    175,000 SH                 X              1       X
INTL PAPER CO                COM            460146103    12,920    475,000 SH                 X              2       X
INTUIT                       COM            461202103       540     20,000 SH                         X      3       X
JOHNSON AND JOHNSON          COM            478160104     1,297     20,000 SH                         X      3       X
KELLOGG                      COM            487836108     1,051     20,000 SH                         X      3       X
KRAFT FOODS INC              CL A           50075N104     6,512    210,000 SH                 X              1       X
KRAFT FOODS INC              CL A           50075N104    20,777    670,000 SH                 X              2       X
LAUDER ESTEE COS INC         CL A           518439104     1,146     25,000 SH                         X      3       X
LEGGETT & PLATT INC          COM            524660107     8,083    530,000 SH                 X              1       X
LEGGETT & PLATT INC          COM            524660107    22,417  1,470,000 SH                 X              2       X
LILLY ELI & CO               COM            532457108     1,548     30,000 SH                         X      3       X
LINCOLN NATIONAL CORP IND    COM            534187109       934     17,963 SH                         X      3       X



                                                                               1



SECURITIES AND EXCHANGE COMMISSIONS FORM 13F INFORMATION
PREPARED FOR ALLEGHANY CORPORATION
AS OF 03/31/08



          COLUMN 1              COLUMN 2     COLUMN 3  COLUMN 4       COLUMN 5             COLUMN 6       COLUMN 7    COLUMN 8
       --------------        -------------- --------- --------- ------------------- --------------------- -------- --------------
                                                                                          INVESTMENT                   VOTING
                                                        MARKET                            DISCRETION                  AUTHORITY
                                                        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)
       --------------        -------------- --------- --------- ---------- --- ---- ---- ---------- ----- -------- ---- ---- ----
                                                                                      
MANPOWER INC                 COM            56418H100       844     15,000 SH                         X      3       X
MEDTRONIC INC                COM            585055106     1,451     30,000 SH                         X      3       X
MERRILL LYNCH & CO INC       COM            590188108     4,889    120,000 SH                 X              1       X
MERRILL LYNCH & CO INC       COM            590188108    11,407    280,000 SH                 X              2       X
MICROSOFT CORP               COM            594918104     2,129     75,000 SH                         X      3       X
MILLIPORE CORP               COM            601073109     1,348     20,000 SH                         X      3       X
NEWS CORP                    CL A           65248E104     1,313     70,000 SH                         X      3       X
NOBLE ENERGY INC             COM            655044105     2,184     30,000 SH                         X      3       X
NORDSTROM INC                COM            655664100       978     30,000 SH                         X      3       X
NOVARTIS AG                  SPONSORED ADR  66987V109     1,281     25,000 SH                         X      3       X
OLD REP INTL CORP            COM            680223104     1,937    150,000 SH                 X              1       X
OLD REP INTL CORP            COM            680223104     1,291    100,000 SH                 X              2       X
OLD REP INTL CORP            COM            680223104    18,074  1,400,000 SH                 X              3       X
PHH CORP                     COM            693320202     6,916    396,800 SH                 X              3       X
PNM RES INC                  COM            69349H107     1,559    125,000 SH                 X              1       X
PNM RES INC                  COM            69349H107     4,676    375,000 SH                 X              2       X
PFIZER INC                   COM            717081103     6,802    325,000 SH                 X              1       X
PFIZER INC                   COM            717081103    14,128    675,000 SH                 X              2       X
PROCTER & GAMBLE CO          COM            742718109     2,102     30,000 SH                         X      3       X
SCHLUMBERGER LTD             COM            806857108     2,175     25,000 SH                         X      3       X
SIGMA ALDRICH CORP           COM            826552101     1,790     30,000 SH                         X      3       X
SONY CORP                    ADR NEW        835699307     1,002     25,000 SH                         X      3       X
STATE STR CORP               COM            857477103     1,185     15,000 SH                         X      3       X
SUNOCO INC                   COM            86764P109     3,673     70,000 SH                 X              1       X
SUNOCO INC                   COM            86764P109     1,574     30,000 SH                 X              2       X
SYSCO CORP                   COM            871829107       871     30,000 SH                         X      3       X
TALISMAN ENERGY INC          COM            87425E103     4,043    228,400 SH                 X              1       X
TESORO CORP                  COM            881609101    12,750    425,000 SH                 X              2       X
TEXAS INSTRS INC             COM            882508104       565     20,000 SH                         X      3       X
3M CO                        COM            88579Y101     1,741     22,000 SH                         X      3       X
VALERO ENERGY CORP NEW       COM            91913Y100     7,858    160,000 SH                 X              1       X
VALERO ENERGY CORP NEW       COM            91913Y100    15,224    310,000 SH                 X              2       X
WACHOVIA CORP 2ND NEW        COM            929903102     3,037    112,500 SH                 X              1       X
WACHOVIA CORP 2ND NEW        COM            929903102     8,303    307,500 SH                 X              2       X
WACHOVIA CORP 2ND NEW        COM            929903102     1,080     40,000 SH                         X      3       X
WAL MART STORES INC          COM            931142103     2,371     45,000 SH                         X      3       X
WASHINGTON POST CO           CL B           939640108       992      1,500 SH                         X      3       X
WELLS FARGO & CO NEW         COM            949746101     3,434    118,000 SH                 X              1       X
WELLS FARGO & CO NEW         COM            949746101     9,370    322,000 SH                 X              2       X
WELLS FARGO & CO NEW         COM            949746101       582     20,000 SH                         X      3       X
WEYERHAUSER CO               COM            962166104     1,301     20,000 SH                         X      3       X
WYETH                        COM            983024100     3,550     85,000 SH                 X              1       X
WYETH                        COM            983024100     7,934    190,000 SH                 X              2       X
ZENITH NATL INS CORP         COM            989390109    14,110    393,475 SH                 X              3       X

GRAND TOTAL                                           1,232,881 30,767,656



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