FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * TJIAN HANS T Y   2. Issuer Name and Ticker or Trading Symbol WESTAMERICA BANCORPORATION [WABC] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) Exec. Off. Primary Subsidiary (Last) (First) (Middle) 3. Date of Earliest Transaction (Month/Day/Year) 04/01/2005 (Street)   4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 04/01/2005   F   2,275 (1) D $ 50.8289 19,870 (1) I Deferred Common Stock               21,026.716 (2) I ESOP Common Stock               43 I by Son Common Stock               21,190.4092 (1) (3) I by Trust Common Stock               2,490.42 I by self cust daughter 1 Common Stock               27,220.72 (3) I self--IRA Common Stock               1,850 I wife cust daughter 2 Common Stock               5,550 I wife cust son 25 Common Stock               1,690 I wife--IRA

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
TJIAN HANS T Y			Exec. Off. Primary Subsidiary

Signatures

by Hans T.Y. Tjian		04/05/2005
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	The reporting person deferred delivery of 6,630 restricted performance shares vesting in January 2003 until March 31, 2005. The shares were held in a rabbi trust ("Deferred") until the prescheduled distribution. At the time of the distribution from the rabbi trust, 4,355 shares were delivered to the reporting person's trust and 2,275 shares were sold by the rabbi trust to pay the tax liability. Also, since the reporting person's last report, 3,070 restricted performance shares vesting 1/26/05 and held as a direct holding until delivery, was delivered to the reporting person's deferred holdings.
(2)	Includes all contributions to Westamerica Bancorporation's Tax Deferred/Savings Plan (ESOP) through 3/31/05.
(3)	Includes reinvested dividends as of 2/7/05.

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