For Shareholders

HAMILTON, Bermuda, May 16 /PRNewswire-FirstCall/ -- White Mountains Insurance Group, Ltd. ("White Mountains") (NYSE: WTM) announced today that its wholly-owned subsidiary, White Mountains Re Group, Ltd. ("White Mountains Re"), intends to offer and sell 250,000 fixed/floating perpetual non-cumulative preference shares, liquidation preference $1,000 per share (the "Preference Shares"), in an offering exempt from the registration requirements of the Securities Act of 1933, as amended (the "Securities Act").

White Mountains Re intends to use the net proceeds from the offering of the Preference Shares to further capitalize its reinsurance subsidiaries, including its Bermuda platform, and for general corporate purposes.

The Preference Shares will be sold only to qualified institutional buyers in reliance on Rule 144A and outside the United States to non-U.S. persons in reliance on Regulation S. The Preference Shares have not and will not be registered under the Securities Act, and, unless so registered, may not be offered or sold in the United States except pursuant to an exemption from, or in a transaction not subject to, the registration requirements of the Securities Act and applicable state securities laws.

This press release shall not constitute an offer to sell or the solicitation of an offer to buy, nor shall there be any sale of the Preference Shares in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

                            ADDITIONAL INFORMATION

White Mountains is a Bermuda-domiciled financial services holding company traded on the New York Stock Exchange and the Bermuda Stock Exchange under the symbol WTM. Additional financial information and other items of interest are available at the Company's web site located at http://www.whitemountains.com.

 Safe Harbor Statement under the Private Securities Litigation Reform Act of
                                     1995

The press release may contain "forward-looking statements" within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. All statements, other than statements of historical facts, included or referenced in this release which address activities, events or developments which we expect or anticipate will or may occur in the future are forward-looking statements. The words "will," "believe," "intend," "expect," "anticipate," "project," "estimate," "predict" and similar expressions are also intended to identify forward-looking statements. These forward-looking statements include, among others, statements with respect to White Mountains':

      -- growth in book value per share or return on equity;
      -- business strategy;
      -- financial and operating targets or plans;
      -- incurred losses and the adequacy of its loss and loss adjustment
         expense reserves and related reinsurance;
      -- projections of revenues, income (or loss), earnings (or loss) per
         share, dividends, market share or other financial forecasts;
      -- expansion and growth of our business and operations; and
      -- future capital expenditures.

These statements are based on certain assumptions and analyses made by White Mountains in light of its experience and perception of historical trends, current conditions and expected future developments, as well as other factors believed to be appropriate in the circumstances. However, whether actual results and developments will conform to our expectations and predictions is subject to a number of risks and uncertainties that could cause actual results to differ materially from expectations, including:

      -- the risks described in Item 1A of White Mountains' 2006 Annual Report
         on Form 10-K;
      -- claims arising from catastrophic events, such as hurricanes,
         earthquakes, floods or terrorist attacks;
      -- the continued availability of capital and financing;
      -- general economic, market or business conditions;
      -- business opportunities (or lack thereof) that may be presented to it
         and pursued;
      -- competitive forces, including the conduct of other property and
         casualty insurers and reinsurers;
      -- changes in domestic or foreign laws or regulations, or their
         interpretation, applicable to White Mountains, its competitors or its
         clients;
      -- an economic downturn or other economic conditions adversely affecting
         its financial position;
      -- recorded loss reserves subsequently proving to have been inadequate;
      -- other factors, most of which are beyond White Mountains' control.

Consequently, all of the forward-looking statements made in this press release are qualified by these cautionary statements, and there can be no assurance that the actual results or developments anticipated by White Mountains will be realized or, even if substantially realized, that they will have the expected consequences to, or effects on, White Mountains or its business or operations. White Mountains assumes no obligation to update publicly any such forward-looking statements, whether as a result of new information, future events or otherwise.

CONTACT: David Foy of White Mountains Insurance Group, Ltd.,
+1-203-458-5850

SOURCE White Mountains Insurance Group, Ltd. /Web site: http://www.whitemountains.com /