Alterra Capital Holdings Limited ("Alterra") (NASDAQ: ALTE; BSX: ALTE.BH) today announced that it expects to record fourth quarter 2011 losses from catastrophe events of approximately $50 million, including an initial loss estimate from the severe flooding in Thailand during the fourth quarter of approximately $30 million, pretax and net of reinsurance and reinstatement premiums. It is expected that losses from the Thai event will largely relate to claims for contingent business interruption. The remaining catastrophe losses recorded in the fourth quarter principally relate to the Japanese Earthquake and Tsunami event.

Alterra's loss estimates are based on proprietary modeling analyses, industry assessments of exposure, claims information obtained from Alterra's clients and brokers to date, and a review of in-force contracts. Alterra's actual losses from these events may vary materially from the estimates due to the inherent uncertainties in making such determinations resulting from several factors, including the preliminary nature of available information, the potential inaccuracies and inadequacies in the data provided by clients and brokers, the modeling techniques employed and the application of such techniques, the contingent nature of business interruption exposures, the effects of any resultant demand surge on claims activity, and attendant coverage issues. In addition, actual losses may increase if Alterra's reinsurers fail to meet their obligations to Alterra or the reinsurance protections purchased by Alterra are exhausted or are otherwise unavailable.

About Alterra Capital Holdings Limited

Alterra Capital Holdings Limited is a global enterprise dedicated to providing diversified specialty insurance and reinsurance products to corporations, public entities, and property and casualty insurers.

Cautionary Note Regarding Forward-Looking Statements

This release includes forward-looking statements that reflect Alterra's current views with respect to future events and financial performance. These forward-looking statements are subject to certain risks and uncertainties that could cause actual results to differ materially from those suggested by such statements. For further information regarding cautionary statements and factors affecting Alterra's future results, please refer to the most recent reports on Form 10-K and Form 10-Q and other documents filed by Alterra with the SEC. Alterra undertakes no obligation to update or revise publicly any forward-looking statement whether as a result of new information, future developments or otherwise.

Alterra Capital Holdings Limited
Susan Spivak Bernstein, 1-212-898-6640
Senior Vice President
susan.spivak@alterra-bm.com
or
Kekst and Company
Melissa Sheer or Peter Hill, 1-212-521-4800
melissa-sheer@kekst.com / peter-hill@kekst.com