8-K

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549



                                    FORM 8-K


                               |X| CURRENT REPORT

                         PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934



                        Date of Report: December 8, 2003



                        Commission file number 001-15081



                             UnionBanCal Corporation


                        State of Incorporation: Delaware
                  I.R.S. Employer Identification No. 94-1234979



                              400 California Street
                          San Francisco, CA 94104-1302
                               Tel. (415) 765-2969


















Item 5.  Other Events.

On December 8, 2003, UnionBanCal Corporation issued a press release concerning
Regulatory Approval Granted for Union Bank of California to Acquire Business
Bank of California, a copy of which is furnished herewith as Exhibit 99.1.


            Exhibit No.            Description
- --------------------------------------------------------------------------------
                 99.1              Text of press release dated December 8, 2003.













                                    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, thereunto duly authorized.


Dated:   December 8, 2003


                          UNIONBANCAL CORPORATION


                          By:       /s/  DAVID I. MATSON
                                --------------------------------
                                      David I. Matson
                                   Chief Financial Officer
                                   (Duly Authorized Officer)

EX-99

                                                                   Exhibit 99.1

Regulatory Approval Granted for Union Bank of California, N.A. to
Acquire Business Bank of California

    SAN FRANCISCO & SAN RAFAEL, Calif.--(BUSINESS WIRE)--Dec. 8,
2003--UnionBanCal Corporation (NYSE: UB), parent company of Union Bank
of California, N.A., jointly announced today with Business Bancorp
(NASDAQ: BZBC), parent company of Business Bank of California, that
the Office of the Comptroller of the Currency and the Federal Deposit
Insurance Corporation have granted approval for the merger of Business
Bank of California with and into Union Bank.
    Shareholders of Business Bancorp will vote on the transaction at a
special meeting of shareholders scheduled for January 12, 2004. The
transaction is expected to close on or before January 31, 2004. Under
the terms of the agreement, each share of Business Bancorp stock will
be exchanged -- at each shareholder's election -- either for cash of
$28.57 per share or for an amount of UnionBanCal Corporation common
stock determined by an exchange ratio detailed in the merger
documents.
    Business Bank is a $676 million commercial bank headquartered in
San Bernardino, California, with approximately 235 employees and
fifteen full-service branches in two distinct markets -- the Southern
California Inland Empire and the San Francisco Bay Area. Business
Bank's ten Southern California branches are located in the cities of
Corona, Hemet, Hesperia, Ontario, Phelan, Redlands, Riverside, San
Bernardino (2) and Upland. Business Bank's five Bay Area branches are
located in the cities of Hayward, Petaluma, San Francisco, South San
Francisco and San Rafael.
    Based in San Francisco, UnionBanCal Corporation is a bank holding
company with assets of $42.6 billion at September 30, 2003. Its
primary subsidiary, Union Bank of California, N.A., currently has 278
banking offices in California, 4 banking offices in Oregon and
Washington, and 20 international facilities. The web site is located
at www.uboc.com.

    This communication is not a solicitation of a proxy from any
security holder of Business Bancorp. Business Bancorp, and its
directors and executive officers and other members of its management
and employees, may be deemed to be participants in the solicitation of
proxies from the shareholders of Business Bancorp in connection with
the merger. Information about the directors and executive officers of
Business Bancorp and their ownership in Business Bancorp stock is set
forth in the proxy statement/prospectus. Employment and compensation
agreements of certain potential participants, including salary
continuation agreements and change of control agreements, are filed as
exhibits to the Business Bancorp Form 10-K for the year ended December
31, 2002 and Form 10-Q for the quarter ended September 30, 2003 and
described in the proxy statement/prospectus. Investors may obtain
additional information regarding the interests of the participants by
reading the proxy statement/prospectus relating to the merger.
    Shareholders of Business Bancorp and other investors are urged to
read the proxy statement/prospectus included in the registration
statement on Form S-4, which UnionBanCal has filed with the SEC in
connection with the proposed merger. The Form S-4 contains important
information about UnionBanCal, Union Bank of California, Business
Bancorp, Business Bank of California, the merger, the persons
soliciting proxies in the merger and their interests in the merger and
related matters. The proxy statement/prospectus is available for free,
both on the SEC web site (http://www.sec.gov) and from John A. Rice,
Jr., SVP, UnionBanCal Corporation Investor Relations at (415)
765-2969, or Patrick Phelan, Chief Financial Officer of Business
Bancorp, at (415) 459-2265.

    Forward-Looking Statements

    The following appears in accordance with the Private Securities
Litigation Reform Act: This press release includes forward-looking
statements that involve risks and uncertainties. Forward-looking
statements can be identified by looking at the fact that they do not
relate strictly to historical or current facts, and often include the
words "believe," "expect," "anticipate," or "project," or words of
similar meaning, or future or conditional verbs such as "will,"
"would," "should," "could," or "may." These forward looking statements
include, but are not limited to, statements regarding the expected
benefits of the transaction, the likelihood and timing of the closing
of the transaction and the final valuation of the merger. A number of
important factors could cause actual results to differ materially from
those in the forward-looking statements. Those factors include, but
are not limited to, when and if the transaction is consummated, the
approval of Business Bancorp shareholders of the merger agreement,
fluctuations in UnionBanCal's stock price, and other related risk
factors, are included in the public filings of the Companies with the
Securities and Exchange Commission, which are available online at
http://www.sec.gov. All forward-looking statements included in this
press release are based on information available at the time of the
release, and neither UnionBanCal Corporation nor Business Bancorp
assumes any obligation to update any forward-looking statement.

    CONTACT: UnionBanCal Corporation
             John A. Rice, Jr., 415-765-2969
             SVP -- Investor Relations
             Steven Johnson, 415-765-3252
             SVP -- Public Relations
             or
             Business Bancorp
             Alan Lane, 909-888-2265
             Chief Executive Officer
             Patrick E. Phelan, 415-459-2265
             Chief Financial Officer