Westamerica Bank

September 14, 2006

For Immediate Release

San Rafael, CA: Westamerica Bancorporation (NASDAQ: WABC), parent company of Westamerica Bank, 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, 2007.

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."

The repurchase plan represents approximately 6.4% of the Company’s common stock outstanding as of August 1, 2006, as reported on the Company's most recent Form 10-Q filed with the Securities and Exchange Commission (SEC) on August 4, 2006. This plan replaces the existing two million-share stock repurchase program authorized in August 2005, under which 561 thousand shares remained available to purchase as of June 30, 2006. The Company routinely reports activity under stock repurchase plans on periodic Form 10-Q and Form 10-K filings with the SEC.

Westamerica Bancorporation, through its wholly owned subsidiary Westamerica Bank, operates 87 branches and two trust offices throughout 21 counties in Northern and Central California. At June 30, 2006, total assets were $4.9 billion and shareholders’ equity was $421 million.