Westamerica Bank

April 18, 2006

For Immediate Release

San Rafael, CA: Westamerica Bancorporation (NASDAQ: WABC), parent company of Westamerica Bank, today reported quarterly net income for the first quarter of 2006 of $26.1 million or $0.81 diluted earnings per share compared to $22.3 million or $0.68 diluted earnings per share for the first quarter of 2005. Prior year results reflect the retrospective adoption of Statement of Financial Accounting Standard 123 (revised), which requires recognition of compensation expense for equity awards to employees. First quarter 2005 results include one month of operating results following the March 1, 2005 acquisition of Redwood Empire Bancorp. First quarter 2005 results also include a loss on sale of available-for-sale investment securities totaling $2.8 million, net of tax, or $0.08 per diluted share outstanding.

"We are very pleased with first quarter results, given the difficult interest rate environment. Profitability levels remain high with first quarter 2006 return on equity of 24.9 percent and return on assets of 2.10 percent," said Chairman, President and CEO David Payne. "Our low cost of funds, low credit costs, improved fee income, and low cost structure result in net income equal to 38.6 percent of revenues," added Payne.

Net interest income on a fully taxable equivalent (FTE) basis was $54.0 million in the first quarter of 2006, compared to $55.8 million in the prior quarter and to $55.0 million in the first quarter of 2005. The first quarter 2006 net interest margin on a fully taxable equivalent basis was 4.73 percent, compared to 4.80 percent in the prior quarter and 4.90 percent for the first quarter of 2005.

The provision for loan losses was $150 thousand for the first quarter of 2006, compared to $150 thousand in the previous quarter, and $300 thousand in the first quarter of 2005. Net loan losses totaled $231 thousand or 0.04 percent of average loans (annualized) in the first quarter of 2006.

Noninterest income in the first quarter of 2006 totaled $13.6 million compared to $7.2 million in the first quarter 2005, which included a $4.9 million loss on sale of investment securities. Merchant credit card income increased $1.1 million in the first quarter 2006 compared to the year ago period primarily due to the acquired merchant card servicing business of Redwood Empire Bancorp on March 1, 2005. Debit card fees were also higher than the year ago period due to higher activity levels.

Noninterest expense for the first quarter of 2006 totaled $25.5 million, $1.5 million lower than the previous quarter, and $400 thousand lower than the first quarter of 2005. The decrease from the prior quarter is primarily due to lower personnel costs, professional fees, and operational losses. The decrease from the first quarter of 2005 is primarily due to lower personnel costs and professional fees, offset in part by higher amortization of intangible assets and occupancy costs. The first quarter 2006 efficiency ratio (expenses/revenues) was 37.7 percent compared to 38.4 percent in the prior quarter.

At March 31, 2006, shareholders' equity was $429 million and the equity-to-asset ratio was 8.5 percent. During the first quarter of 2006 repurchases of the Company's common stock totaled approximately 338 thousand shares, net of shares issued.

At March 31, 2006, the Company's assets totaled $5.1 billion and total loans outstanding totaled $2.6 billion.

Westamerica Bancorporation, through its wholly owned subsidiary Westamerica Bank, currently operates 87 branches and two trust offices throughout 21 Northern and Central California counties.


Quarterly Financial Highlights

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-K for the year ended December 31, 2005, 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, and 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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