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

                                    FORM 13F
                               FORM 13F COVER PAGE

       INFORMATION REQUIRED OF INSTITUTIONAL INVESTMENT MANAGERS PURSUANT
  TO SECTION 13(f) OF THE SECURITIES EXCHANGE ACT OF 1934 AND RULES THEREUNDER

     Report for the Calendar Year or Quarter Ended   September 30  , 2000.
                                                   ----------------

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:                                     White Mountains Insurance Group, Ltd.
Address of Principal Executive Office:    80 South Main Street
                                          Hanover, New Hampshire 03755-2053
                                          U.S.A.

Form 13F File Number:                     028-01681

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 therein 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:    Michael S. Paquette
Title:   Senior Vice President and Controller
Phone:   (603) 640-2205

Signature, Place, and Date of Signing:

/s/ Michael S. Paquette      Hanover, New Hampshire          November 14, 2000
- -------------------------   ------------------------       ---------------------
      [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).)

List of Other Managers Reporting for this Manager:

Form 13F File Number  Name
- -                     None



                              FORM 13F SUMMARY PAGE

Report Summary:

Number of Other Included Managers:                          1

Form 13F Information Table Entry Total:                  99 ITEMS
                                                      -------------
Form 13F Information Table Value Total:               $215,715,087
                                                      -------------

List of Other Included Managers:

Provide a numbered list of the names 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. 028-07388 FOLKSAMERICA HOLDING COMPANY, INC. 2. 028-04945 WYPER CAPITAL MANAGEMENT, L.P.
WHITE MOUNTAINS INSURANCE GROUP, LTD. FORM 13F INFORMATION TABLE - SEPTEMBER 30, 2000
------------------------------------------------------------------------------------------------------------------ Title CUSIP Market Name of Issuer of class Number Value ------------------------------------------------------------------------------------------------------------------ 1 Aetna Inc. COM 008117103 345,472 2 Affiliated Computer CL A 008190100 339,150 3 Alleghany Corp Del COM 017175100 552,720 4 Allmerica Financial Corp. COM 19754100 93,477 5 Ambac Inc. COM 023139108 567,688 6 America Online, Inc. COM 02364J104 1,827,500 7 American Express Company COM 025816109 139,725 8 American International Group COM 026874107 4,126,523 9 American International Group COM 026874107 143,531 10 Amgen Inc. COM 031162100 5,237,109 11 Aon Corp. COM 037389103 584,825 12 Asia Satellite Telecommunications SPONSORED ADR 04516X106 282,225 13 Avaya Inc. COM 053499109 88,883 14 Avery Dennison Corp. COM 053611109 73,365 15 Avon Products Inc. COM 054303102 401,147 16 Banc One Corp. COM 06423A103 528,969 17 Berkley, W.R. Corp COM 084423102 203,919 18 Berkshire Hathaway, Inc. Class A CL A 084670108 31,234,000 19 Berkshire Hathaway, Inc. Class B CL B 084670207 1,080,540 20 Berkshire Hathaway, Inc. Class B CL B 084670207 20,327,400 21 BF Goodrich COM 382388106 333,682 22 Bisys Group COM 055472104 195,601 23 Bristol Myers Squibb Co. COM 110122108 2,742,000 24 Cabot Corp COM 127055101 241,807 25 Cabot Microelectronics COM 12709P103 102,720 26 Carnival Corp. COM 143658102 482,650 27 Chase Manhattan Corp. COM 16161A108 351,025 28 Cisco Systems COM 17275R102 6,160,375 29 Citigroup, Inc COM 172967101 5,766,667 30 Citigroup, Inc COM 172967101 678,052 31 Coca Cola Corp COM 191216100 1,598,625 32 Concord EFS Inc. COM 206197105 284,125 33 Corus Entertainment Class B COM CL B NON VTG 220874101 97,840 34 Costco COM 22160K105 2,096,250 35 Dell Computer Corp. COM 247025109 2,773,125 36 Dexia Ords (Belgium Listing) COM 9900004S7 26,800,884 37 Du Pont Nemours COM 263534109 956,295 38 EMC Corporation COM 268648102 9,912,500 39 Federal National Mortgage Assn. COM 313586109 979,550 40 Fidelity National Financial, Inc. COM 316326107 9,306,000 41 First Data Corp. COM 319963104 447,266 42 General Electric Co. COM 369604103 6,576,375 43 General Motors Class H CL H NEW 370442832 97,486 44 General Motors Corp. COM 370442105 454,025 45 Gillette Company COM 375766102 3,241,875 46 Harman International COM 413086109 244,531 47 Home Depot Inc. COM 437076102 69,247 48 Home Depot Inc. COM 437076102 4,080,506 49 IMS Health COM 449934108 527,756 50 IMS Health COM 449934108 419,150 51 Intel Corp. COM 458140100 3,325,000 52 Interlink Electronics COM 458751104 34,972 53 Intl Speedway Corp CL A 460335201 90,870 54 Intuit Inc. COM 461202103 1,254,000 55 Jefferson Pilot Corp. COM 475070108 441,188 56 John Hancock Financials COM 41014S106 846,563 57 Johnson & Johnson COM 478160104 4,509,000 58 Lasalle Re Holdings Ltd. ORD G5383Q101 205,620 59 Lexmark International CL A 529771107 174,113 60 Lexmark International CL A 529771107 1,331,250 61 Liberty Financial Co. COM 530512102 244,400 62 Lincoln National Corp COM 534187109 385,289 63 Lockheed Martin COM 539830109 371,525 64 London Pacific Group Ltd. SPONSORED ADR 542073101 411,413 65 Loral Space & Communications Ltd COM G56462107 306,250 66 Lucent Technologies Inc. COM 549463107 1,421,156 67 Marsh & McLennan Inc. COM 571748102 677,025 68 MCI Worldcom, Inc. COM 55268B106 2,202,188 69 Microsoft Corp COM 594918104 1,628,438 70 Motorola COM 620076109 2,542,500 71 Nordstrom Inc. COM 655664100 778,125 72 Northrop Grumman COM 666807102 512,444 73 Partner Re., Ltd. COM G6852T105 588,225 74 Partner Re., Ltd. COM G6852T105 1,190,065 75 Pfizer Inc. COM 717081103 2,696,250 76 PXRe Group, Ltd. COM 693674103 220,500 77 PXRe Group, Ltd. COM G73018106 5,521,950 78 Qualcomm, Inc. COM 747525103 1,781,250 79 Renaissance Re Holding Ltd. COM G7496G103 786,431 80 Royal Bank of Scotland AVS COM G76893190 18,922 81 Royal Bank of Scotland Group COM G76891111 332,564 82 Ryder Sys Inc. COM 783549108 308,164 83 Safeco Corp. COM 786429100 269,775 84 Schering-Plough Corp. COM 806605101 3,473,550 85 Sealed Air Corp COM 81211K100 16,064 86 Shaw Communications COM 82028K200 15,153 87 Synavant Inc. COM 87157A105 6,754 88 Synavant Inc. COM 87157A105 8,500 89 Time Warner, Inc. COM 887315109 294,377 90 UCAR Intl Inc COM 90262K109 26,720 91 US Bancorp Del COM 902973106 256,802 92 Vesta Insurance Group, Inc. COM 925391104 12,964,064 93 Visteon Corp COM 92839U107 97,904 94 Waddell & Reed Financial Inc. CL A 930059100 148,459 95 Waddell & Reed Financial Inc. CL A 930059100 515,530 96 Wal-Mart Stores, Inc. COM 931142103 2,541,000 97 Waste Management Inc. COM 94106L109 372,029 98 XL Capital, Ltd. CL A G98255105 521,483 99 XL Capital, Ltd. CL A G98255105 853,115 -------------------------- $215,715,087 * 1 = Folksamerica Holding Company, Inc. (FORM 13F filed separately) 2 = Wyper Capital Management, L.P. 3 = White Mountains Insurance Group, Ltd. ----------------------------------------------------------------------------------------------------------------------------- Amount and Investment Voting Authority (Shares) Name of Issuer Type of Security Discretion Managers * Sole Shared None ----------------------------------------------------------------------------------------------------------------------------- 1 Aetna Inc. 5,950 SH DEFINED 1,3 5,950 2 Affiliated Computer 6,800 SH DEFINED 1,3 6,800 3 Alleghany Corp Del 2,820 SH DEFINED 1,3 2,820 4 Allmerica Financial Corp. 1,462 SH DEFINED 2,3 1,462 5 Ambac Inc. 7,750 SH DEFINED 1,3 7,750 6 America Online, Inc. 34,000 SH DEFINED 1,3 34,000 7 American Express Company 2,300 SH DEFINED 1,3 2,300 8 American International Group 43,125 SH DEFINED 1,3 43,125 9 American International Group 1,500 SH DEFINED 2,3 1,500 10 Amgen Inc. 75,000 SH DEFINED 1,3 75,000 11 Aon Corp. 14,900 SH DEFINED 1,3 14,900 12 Asia Satellite Telecommunications 11,289 SH DEFINED 2,3 11,289 13 Avaya Inc. 3,875 SH DEFINED 1,3 3,875 14 Avery Dennison Corp. 1,582 SH DEFINED 2,3 1,582 15 Avon Products Inc. 9,814 SH DEFINED 2,3 9,814 16 Banc One Corp. 13,695 SH DEFINED 2,3 13,695 17 Berkley, W.R. Corp 5,900 SH DEFINED 1,3 5,900 18 Berkshire Hathaway, Inc. Class A 485 SH SOLE 2 485 19 Berkshire Hathaway, Inc. Class B 522 SH DEFINED 1,3 522 20 Berkshire Hathaway, Inc. Class B 9,820 SH SOLE 2 9,820 21 BF Goodrich 8,515 SH DEFINED 2,3 8,515 22 Bisys Group 2,530 SH DEFINED 1,3 2,530 23 Bristol Myers Squibb Co. 48,000 SH DEFINED 1,3 48,000 24 Cabot Corp 7,631 SH DEFINED 2,3 7,631 25 Cabot Microelectronics 2,140 SH DEFINED 2,3 2,140 26 Carnival Corp. 19,600 SH DEFINED 1,3 19,600 27 Chase Manhattan Corp. 7,600 SH DEFINED 1,3 7,600 28 Cisco Systems 111,500 SH DEFINED 1,3 111,500 29 Citigroup, Inc 106,667 SH DEFINED 1,3 106,667 30 Citigroup, Inc 12,542 SH DEFINED 2,3 12,542 31 Coca Cola Corp 29,000 SH DEFINED 1,3 29,000 32 Concord EFS Inc. 8,000 SH DEFINED 1,3 8,000 33 Corus Entertainment Class B 3,418 SH DEFINED 2,3 3,418 34 Costco 60,000 SH DEFINED 1,3 60,000 35 Dell Computer Corp. 90,000 SH DEFINED 1,3 90,000 36 Dexia Ords (Belgium Listing) 180,000 SH DEFINED 1,3 180,000 37 Du Pont Nemours 23,078 SH DEFINED 2,3 23,078 38 EMC Corporation 100,000 SH DEFINED 1,3 100,000 39 Federal National Mortgage Assn. 13,700 SH DEFINED 1,3 13,700 40 Fidelity National Financial, Inc. 376,000 SH DEFINED 1,3 376,000 41 First Data Corp. 11,450 SH DEFINED 1,3 11,450 42 General Electric Co. 114,000 SH DEFINED 1,3 114,000 43 General Motors Class H 2,622 SH DEFINED 2,3 2,622 44 General Motors Corp. 6,985 SH DEFINED 2,3 6,985 45 Gillette Company 105,000 SH DEFINED 1,3 105,000 46 Harman International 6,254 SH DEFINED 2,3 6,254 47 Home Depot Inc. 1,305 SH DEFINED 2,3 1,305 48 Home Depot Inc. 76,900 SH DEFINED 1,3 76,900 49 IMS Health 25,434 SH DEFINED 2,3 25,434 50 IMS Health 20,200 SH DEFINED 1,3 20,200 51 Intel Corp. 80,000 SH DEFINED 1,3 80,000 52 Interlink Electronics 1,805 SH DEFINED 2,3 1,805 53 Intl Speedway Corp 2,330 SH DEFINED 1,3 2,330 54 Intuit Inc. 22,000 SH DEFINED 1,3 22,000 55 Jefferson Pilot Corp. 6,500 SH DEFINED 1,3 6,500 56 John Hancock Financials 31,500 SH DEFINED 1,3 31,500 57 Johnson & Johnson 48,000 SH DEFINED 1,3 48,000 58 Lasalle Re Holdings Ltd. 11,040 SH DEFINED 1,3 11,040 59 Lexmark International 4,643 SH DEFINED 2,3 4,643 60 Lexmark International 35,500 SH DEFINED 1,3 35,500 61 Liberty Financial Co. 10,400 SH DEFINED 1,3 10,400 62 Lincoln National Corp 8,006 SH DEFINED 2,3 8,006 63 Lockheed Martin 11,272 SH DEFINED 2,3 11,272 64 London Pacific Group Ltd. 20,700 SH DEFINED 1,3 20,700 65 Loral Space & Communications Ltd 50,000 SH DEFINED 1,3 50,000 66 Lucent Technologies Inc. 46,500 SH DEFINED 1,3 46,500 67 Marsh & McLennan Inc. 5,100 SH DEFINED 1,3 5,100 68 MCI Worldcom, Inc. 72,500 SH DEFINED 1,3 72,500 69 Microsoft Corp 27,000 SH DEFINED 1,3 27,000 70 Motorola 90,000 SH DEFINED 1,3 90,000 71 Nordstrom Inc. 50,000 SH DEFINED 1,3 50,000 72 Northrop Grumman 5,639 SH DEFINED 2,3 5,639 73 Partner Re., Ltd. 12,400 SH DEFINED 1,3 12,400 74 Partner Re., Ltd. 25,087 SH DEFINED 2,3 25,087 75 Pfizer Inc. 60,000 SH DEFINED 1,3 60,000 76 PXRe Group, Ltd. 14,000 SH DEFINED 1,3 14,000 77 PXRe Group, Ltd. 350,600 SH SOLE 2 350,600 78 Qualcomm, Inc. 25,000 SH DEFINED 1,3 25,000 79 Renaissance Re Holding Ltd. 12,300 SH DEFINED 1,3 12,300 80 Royal Bank of Scotland AVS 15,789 SH DEFINED 2,3 15,789 81 Royal Bank of Scotland Group 15,789 SH DEFINED 2,3 15,789 82 Ryder Sys Inc. 16,714 SH DEFINED 2,3 16,714 83 Safeco Corp. 9,900 SH DEFINED 1,3 9,900 84 Schering-Plough Corp. 74,700 SH DEFINED 1,3 74,700 85 Sealed Air Corp 355 SH DEFINED 2,3 355 86 Shaw Communications 661 SH DEFINED 2,3 661 87 Synavant Inc. 1,010 SH DEFINED 1,3 1,010 88 Synavant Inc. 1,271 SH DEFINED 2,3 1,271 89 Time Warner, Inc. 3,762 SH DEFINED 2,3 3,762 90 UCAR Intl Inc 2,106 SH DEFINED 2,3 2,106 91 US Bancorp Del 11,288 SH DEFINED 2,3 11,288 92 Vesta Insurance Group, Inc. 2,057,788 SH DEFINED 1,3 2,057,788 93 Visteon Corp 6,473 SH DEFINED 2,3 6,473 94 Waddell & Reed Financial Inc. 4,789 SH DEFINED 2,3 4,789 95 Waddell & Reed Financial Inc. 16,630 SH DEFINED 1,3 16,630 96 Wal-Mart Stores, Inc. 52,800 SH DEFINED 1,3 52,800 97 Waste Management Inc. 21,335 SH DEFINED 2,3 21,335 98 XL Capital, Ltd. 7,095 SH DEFINED 1,3 7,095 99 XL Capital, Ltd. 11,607 SH DEFINED 2,3 11,607 --------------- 5,304,344
* 1 = Folksamerica Holding Company, Inc. (FORM 13F filed separately) 2 = Wyper Capital Management, L.P. 3 = White Mountains Insurance Group, Ltd.