UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

---

FORM 8-K

---

CURRENT REPORT

Pursuant to Section 13 or 15(d) of
The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported) September 13, 2012 

---

Westamerica Bancorporation
(Exact name of registrant as specified in its charter)

California	001-09383	94-2156203
(State or other jurisdiction of incorporation)	(Commission File Number)	(IRS Employer Identification No.)

1108 Fifth Avenue, San Rafael, California	94901
(Address of principal executive offices)	(Zip Code)

Registrant's telephone number, including area code:   (707) 863-6000

Not Applicable
(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:
	[   ]	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
	[   ]	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
	[   ]	Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
	[   ]	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

---

Item 8.01. Other Events.

The Registrant provides an Update on its Interest Margin in the attached Exhibit 99.1, which is incorporated herein by reference.

Item 9.01. Financial Statements and Exhibits.

    Exhibit 99.1.       Update on Interest Margin dated September 13, 2012

---

SIGNATURE

    Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

		Westamerica Bancorporation (Registrant)
September 13, 2012 (Date)		/s/   JOHN "ROBERT" THORSON John "Robert" Thorson Senior Vice President and Chief Financial Officer

---

	Exhibit Index
	99.1	Update on Interest Margin dated September 13, 2012