Westamerica to Participate in Lehman Brothers Financial Services Conference

SAN RAFAEL, Calif., Aug. 27, 2008 (GLOBE NEWSWIRE) -- Westamerica Bancorporation
(Nasdaq:WABC) is scheduled to participate in the Lehman Brothers 2008 Financial
Services Conference.

David Payne, Chairman, President and CEO, will make a presentation beginning at
8:15 a.m. ET on Monday, September 8, 2008. Investors and the public can access
the presentation via a webcast at
http://cc.talkpoint.com/LEHM002/090808a_jw/default.asp?entity=west or go to
http://westamerica.com/index.php?option=com_content&view=article&id=356&catid=56
Itemid=192 and follow the links to the webcast.

Westamerica Bancorporation through its wholly owned subsidiary, Westamerica
Bank, operates 86 branches and two trust offices throughout 21 Northern and
Central California counties.

Westamerica Bancorporation Web Address: www.westamerica.com

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, 2008 and Form 10-K for the year ended December 31, 2007, 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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CONTACT: Westamerica Bancorporation
Robert A. Thorson, SVP & Chief Financial Officer
707-863-6840