Westamerica Bank

August 25, 2005

For Immediate Release


San Rafael, CA: Westamerica Bancorporation (NASDAQ: WABC), parent company of Westamerica Bank, today announced that its Board of Directors approved a plan to repurchase, as conditions warrant, up to two million shares of the Company's common stock on the open market or in privately negotiated transactions from time to time prior to September 1, 2006. The repurchase plan represents approximately 6.2% of the Company's currently outstanding common stock. This plan replaces the existing two million-share stock repurchase program authorized in August 2004.

Chairman, President, and CEO David Payne stated, "This stock repurchase program is being adopted to continue to provide management with the flexibility to optimize the Company's use of equity capital and enhance shareholder value.   Westamerica's strong capital position, high level of profitability, and low-risk balance sheet supported the initiation of this new program."

Westamerica Bancorporation is the holding company for Westamerica Bank operating 88 branches and two trust offices throughout 21 counties in Northern and Central California. At June 30, 2005, total assets were $5.2 billion, shareholders' equity was $440 million, and total common shares outstanding were approximately 32.6 million.


FORWARD-LOOKING INFORMATION:

The following appears in accordance with the Private Securities Litigation Reform Act of 1995:

This press release may contain forward-looking statements about the Company, including descriptions of plans or objectives of its management for future operations, products or services, and forecasts of its revenues, earnings or other measures of economic performance. Forward-looking statements can be identified by the fact that they do not relate strictly to historical or current facts. They often include the words "believe," "expect," "anticipate," "intend," "plan," "estimate," or words of similar meaning, or future or conditional verbs such as "will," "would," "should," "could," or "may."

Forward-looking statements, by their nature, are subject to risks and uncertainties. A number of factors - many of which are beyond the Company's control - could cause actual conditions, events or results to differ significantly from those described in the forward-looking statements. The Company's most recent annual and quarterly reports filed with the Securities and Exchange Commission, including the Company's Form 10-Q for the quarter ended June 30, 2005 and Form 10-K for the year ended December 31, 2004, describe some of these factors, including certain credit, market, operational, liquidity and interest rate risks associated with the Company's business and operations. Other factors described in these reports include changes in business and economic conditions, competition, fiscal and monetary policies, disintermediation, legislation including the Sarbanes-Oxley Act of 2002 and the Gramm-Leach-Bliley Act of 1999, the combination of the former Redwood Empire Bancorp and other mergers and acquisitions.

Forward-looking statements speak only as of the date they are made. The Company does not undertake to update forward-looking statements to reflect circumstances or events that occur after the date forward looking statements are made.

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