On May 2, 2017, White Mountains Insurance Group, Ltd. issued a press release announcing its results for the three months ended March 31, 2017. The press release furnished herewith is attached as Exhibit 99.1 to this Form 8-K. Certain information included in the press release constitutes non-GAAP financial measures (as defined in Regulation G of the Securities and Exchange Commission). Specifically, non-GAAP financial measures disclosed in the press release are adjusted book value per share and investment returns on common equity and other long-term investments including high-yield fixed maturity investments.

Adjusted book value per share is a non-GAAP financial measure which is derived by adjusting the GAAP book value per share denominator to exclude unearned restricted common shares, the compensation cost of which, at the date of calculation, has yet to be amortized. In addition, the calculation of adjusted book value per share includes the dilutive effects of outstanding non-qualified options for periods prior to January 20, 2017, the expiration date of the non-qualified options. A schedule is included in Exhibit 99.1 to this Form 8-K that reconciles GAAP book value per share to adjusted book value per share.

In the third quarter of 2016, White Mountains purchased high-yield fixed maturity investments, which are U.S. dollar denominated publicly traded and 144A debt securities issued by corporations with generally at least one rating between “B-” and “BB+” inclusive by Standard and Poor’s or similar ratings from other rating agencies. Given the risk profile of these investments, White Mountains has included returns on high-yield fixed maturity investment returns with returns on common equity securities and other long-term investments. A schedule is included in Exhibit 99.1 to this Form 8-K that reconciles these investment returns to GAAP investment returns.

ITEM 9.01. FINANCIAL STATEMENTS AND EXHIBITS.

(d) Exhibits

99.1 Press Release of White Mountains Insurance Group, Ltd. dated May 2, 2017, furnished herewith.

About WHITE MOUNTAINS INSURANCE GROUP, LTD. (NYSE:WTM)

White Mountains Insurance Group, Ltd. is an insurance holding company. The Company’s segments include OneBeacon, HG Global/BAM and Other Operations. Its principal businesses are conducted through its insurance, reinsurance and insurance services subsidiaries and affiliates. Its OneBeacon segment consists of OneBeacon Insurance Group, Ltd., which owns a family of property and casualty insurance companies (collectively, OneBeacon). OneBeacon is a specialty property and casualty insurance writer that offers a range of insurance products in the United States primarily through independent agencies, regional and national brokers, wholesalers and managing general agencies. The HG Global/BAM segment consists of HG Global Ltd. (HG Global) and Build America Mutual Assurance Company (BAM). BAM provides insurance on municipal bonds issued to support the United States public purposes, such as schools. Its Other Operations segment consists of the Company and its intermediate holding companies.

WHITE MOUNTAINS INSURANCE GROUP, LTD. (NYSE:WTM) Recent Trading Information

WHITE MOUNTAINS INSURANCE GROUP, LTD. (NYSE:WTM) closed its last trading session down -7.22 at 849.92 with 20,000 shares trading hands.