UNIONBANCAL CORP
S-3, 1998-11-19
NATIONAL COMMERCIAL BANKS
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<PAGE>
   AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON NOVEMBER 19, 1998
  REGISTRATION NOS. 333-      , 333-      , 333-      , 333-      , 333-
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                            ------------------------
 
                                    FORM S-3
 
                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933
                            ------------------------
 
<TABLE>
<S>                              <C>                            <C>
UNIONBANCAL CORPORATION                   CALIFORNIA               94-1234979
UNIONBANCAL FINANCE TRUST I                DELAWARE                94-3313816
UNIONBANCAL FINANCE TRUST II               DELAWARE                94-3313838
UNIONBANCAL FINANCE TRUST III              DELAWARE                94-3313845
UNIONBANCAL FINANCE TRUST IV               DELAWARE                94-3313846
(Exact name of Registrant as     (State or other jurisdiction   (I.R.S. Employer
specified in its charter)            of incorporation or         Identification
                                        organization)                 No.)
</TABLE>
 
                            ------------------------
 
                             350 CALIFORNIA STREET
                        SAN FRANCISCO, CALIFORNIA 94104
                                  415-765-2969
              (Address, Including Zip Code, and Telephone Number,
       Including Area Code, of Registrant's Principal Executive Offices)
                            ------------------------
 
                             JOHN H. MCGUCKIN, JR.
                            EXECUTIVE VICE PRESIDENT
                            UNIONBANCAL CORPORATION
                             400 CALIFORNIA STREET
                        SAN FRANCISCO, CALIFORNIA 94104
                                  415-765-2969
 (Name, Address, Including Zip Code, and Telephone Number, Including Area Code,
                             of Agents for Service)
 
                                    Copy to:
                                 GREGG A. NOEL
                    SKADDEN, ARPS, SLATE, MEAGHER & FLOM LLP
                             300 SOUTH GRAND AVENUE
                         LOS ANGELES, CALIFORNIA 90071
                                 (213) 687-5000
                            ------------------------
 
        APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC:
   FROM TIME TO TIME AFTER THE EFFECTIVE DATE OF THIS REGISTRATION STATEMENT.
                            ------------------------
 
    If the only securities being registered on this Form are being offered
pursuant to dividend or interest reinvestment plans, check the following
box.  / /
 
    If any of the securities being registered on this Form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act,
other than securities offered only in connection with dividend or interest
reinvestment plans, check the following box.  /X/
 
    If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following box
and list the Securities Act registration statement number of the earlier
effective registration statement for the same offering.  / /
 
    If this Form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering.  / /
 
    If delivery of the prospectus is expected to be made pursuant to Rule 434,
please check the following box:  /X/
                            ------------------------
 
THE REGISTRANTS HEREBY AMEND THIS REGISTRATION STATEMENT ON SUCH DATE OR DATES
AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANTS SHALL FILE
A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION STATEMENT
SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(A) OF THE
SECURITIES ACT OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME EFFECTIVE ON
SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(A), MAY
DETERMINE.
 
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- --------------------------------------------------------------------------------
<PAGE>
                        CALCULATION OF REGISTRATION FEE
 
<TABLE>
<CAPTION>
                                                                      PROPOSED            PROPOSED
                                                                      MAXIMUM             MAXIMUM
                                                                     AGGREGATE           AGGREGATE           AMOUNT OF
          TITLE OF EACH CLASS OF                AMOUNT TO BE         PRICE PER            OFFERING        REGISTRATION FEE
      SECURITIES TO BE REGISTERED (1)        REGISTERED (1)(2)      UNIT (2)(3)          PRICE (2)              (4)
<S>                                          <C>                 <C>                 <C>                 <C>
Common Stock of UnionBanCal Corporation....
Preferred Stock of UnionBanCal
  Corporation..............................
Depositary Shares representing Preferred
  Stock of UnionBanCal Corporation (5).....
Preferred Securities of UnionBanCal Finance
  Trust I, UnionBanCal Finance Trust II,
  UnionBanCal Finance Trust III and
  UnionBanCal Finance Trust IV.............     $750,000,000            (3)             $750,000,000          $208,500
Senior debt securities, senior subordinated
  debt securities, subordinated debt
  securities and junior subordinated debt
  securities (collectively, "Debt
  Securities") of UnionBanCal
  Corporation..............................
Guarantee of Preferred Securities of
  UnionBanCal Finance Trust I, UnionBanCal
  Finance Trust II, UnionBanCal Finance
  Trust III and UnionBanCal Finance Trust
  IV, by UnionBanCal Corporation (6).......
Total......................................     $750,000,000            100%            $750,000,000          $208,500
</TABLE>
 
(1) Such indeterminate number of shares of Common Stock, Preferred Stock and
    Depositary Shares and such indeterminate principal amount of Debt Securities
    and such indeterminate number of Preferred Securities of UnionBanCal Finance
    Trust I, UnionBanCal Finance Trust II, UnionBanCal Finance Trust III and
    UnionBanCal Finance Trust IV as may from time to time be issued at
    indeterminate prices. Debt Securities may be issued and sold to UnionBanCal
    Finance Trusts I, II, III and IV, in which event such Debt Securities may
    later be distributed to the holders of trust preferred securities upon a
    dissolution of UnionBanCal Finance Trusts I, II, III and IV and the
    distribution of the assets thereof.
 
(2) The aggregate public offering price of the securities registered hereby will
    not exceed $750,000,000. Any securities registered hereunder may be sold
    separately or as units with other securities registered hereunder.
 
(3) The proposed maximum offering price per unit (a) has been omitted pursuant
    to Instruction II.D. of Form S-3 and (b) will be determined from time to
    time by the Registrants in connection with the issuance of securities
    registered hereunder.
 
(4) Calculated pursuant to Rule 457(o) of the rules and regulations under the
    Securities Act of 1933.
 
(5) Such indeterminate number of Depositary Shares to be evidence by Depositary
    Receipts issued under a Deposit Agreement. If fractional interests in shares
    of Preferred Stock are issued, Depositary Receipts will be distributed for
    such fractional interests and the shares of Preferred Stock will be issued
    to the depositary under the Deposit Agreement.
 
(6) Includes the rights of holders of the trust preferred securities and certain
    back-up obligations of UnionBanCal Corporation as further described in this
    Registration Statement. No separate consideration will be received for any
    Guarantees or the back-up obligations.
<PAGE>
                             SUBJECT TO COMPLETION
                 PRELIMINARY PROSPECTUS DATED NOVEMBER 19, 1998
THE INFORMATION IN THIS PROSPECTUS IS NOT COMPLETE AND MAY BE CHANGED. THESE
SECURITIES MAY NOT BE SOLD UNTIL THE REGISTRATION STATEMENT FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION IS EFFECTIVE. THIS PROSPECTUS IS NOT AN OFFER
TO SELL THESE SECURITIES AND THE COMPANY IS NOT SOLICITING AN OFFER TO BUY THESE
SECURITIES IN ANY STATE WHERE SUCH OFFER OF SALE IS NOT PERMITTED.
<PAGE>
PROSPECTUS
$750,000,000
 
<TABLE>
<S>                                            <C>
UNIONBANCAL CORPORATION                        UNIONBANCAL FINANCE TRUST I
                                               UNIONBANCAL FINANCE TRUST II
                                               UNIONBANCAL FINANCE TRUST III
                                               UNIONBANCAL FINANCE TRUST IV
 
COMMON STOCK, PREFERRED STOCK, DEPOSITARY
SHARES                                         TRUST PREFERRED SECURITIES GUARANTEED BY
AND DEBT SECURITIES                            UNIONBANCAL CORPORATION
</TABLE>
 
- --------------------------------------------------------------------------------
 
THE COMPANY
 
    - may sell common stock to the public;
 
    - may sell preferred stock to the public;
 
    - may sell depositary shares representing preferred stock to the public;
 
    - may sell debt securities to the public; and
 
    - will guarantee the payment by each trust of any trust preferred
      securities.
 
THE TRUSTS
 
    UnionBanCal Finance Trust I, UnionBanCal Finance Trust II, UnionBanCal
Finance Trust III and UnionBanCal Finance Trust IV are Delaware business trusts.
Each trust may:
 
    - sell trust preferred securities (representing undivided beneficial
      interests in the trust) to the public;
 
    - sell trust common securities (representing undivided beneficial interests
      in the trust) to UnionBanCal Corporation;
 
    - use the proceeds from these sales to buy an equal amount of debt
      securities of UnionBanCal Corporation; and
 
    - distribute the cash payments it receives on the debt securities it owns to
      the holders of the trust preferred and trust common securities.
 
    WE URGE YOU TO READ CAREFULLY THIS PROSPECTUS AND THE ACCOMPANYING
PROSPECTUS SUPPLEMENT, WHICH WILL DESCRIBE THE SPECIFIC TERMS OF THE SECURITIES
BEING OFFERED TO YOU, BEFORE YOU MAKE YOUR INVESTMENT DECISION.
 
- --------------------------------------------------------------------------------
 
NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR DETERMINED IF THIS
PROSPECTUS OR THE ACCOMPANYING PROSPECTUS SUPPLEMENT IS TRUTHFUL OR COMPLETE.
ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.
- --------------------------------------------------------------------------------
 
    THIS PROSPECTUS MAY NOT BE USED TO SELL SECURITIES UNLESS ACCOMPANIED BY A
PROSPECTUS SUPPLEMENT.
 
                The date of this prospectus is            , 199
<PAGE>
                               TABLE OF CONTENTS
<TABLE>
<CAPTION>
                                                    PAGE
                                                    -----
<S>                                              <C>
About This Prospectus..........................           2
 
Where You Can Find More Information............           2
 
Special Note Regarding Forward-Looking
  Statements...................................           3
 
The Company....................................           4
 
The Trusts.....................................           8
 
Risk Factors...................................           9
 
Use of Proceeds................................          12
 
Ratio of Earnings to Combined Fixed Charges and
  Preferred Stock Dividends....................          13
 
<CAPTION>
                                                    PAGE
                                                    -----
<S>                                              <C>
 
Description of Securities......................          13
  Description of Capital Stock.................          13
  Description of Depositary Shares.............          15
  Description of the Trust Preferred
    Securities.................................          17
  Description of Debt Securities...............          23
  Description of the Trust Preferred Securities
    Guarantees.................................          30
 
Relationship Among the Trust Preferred
  Securities, the Trust Preferred Securities
  Guarantee and the Debt Securities Held by
  Each Trust...................................          33
 
Plan of Distribution...........................          33
 
Legal Opinion..................................          34
 
Experts........................................          34
</TABLE>
 
                             ABOUT THIS PROSPECTUS
 
    This prospectus is part of a registration statement that we and the trusts
filed with the Securities and Exchange Commission (the "SEC") using a "shelf"
registration process. Under this shelf process, we may sell any combination of
the securities described in this prospectus in one or more offerings up to a
total dollar amount of $750,000,000. This prospectus provides you with a general
description of the securities we may offer. Each time we sell securities, we
will provide a prospectus supplement that will contain specific information
about the terms of that offering. The prospectus supplement may also add, update
or change information contained in this prospectus. You should read both this
prospectus and any prospectus supplement together with additional information
described under the heading "Where You Can Find More Information."
 
                      WHERE YOU CAN FIND MORE INFORMATION
 
    We file reports, proxy statements, and other information with the SEC. Such
reports, proxy statements, and other information concerning UnionBanCal
Corporation can be read and copied at the SEC's Public Reference Room at 450
Fifth Street, N.W., Washington, D.C. 20549. Please call the SEC at
1-800-SEC-0330 for further information on the Public Reference Room. The SEC
maintains an internet site at http://www.sec.gov that contains reports, proxy
and information statements and other information regarding issuers that file
electronically with the SEC, including UnionBanCal Corporation. Our common stock
is quoted on the Nasdaq Stock Market's National Market System ("NMS"). These
reports, proxy statements and other information are also available for
inspection at the offices of the National Association of Securities Dealers,
Inc., Report Section, 1735 K Street N.W., Washington, D.C. 20006.
 
    This prospectus is part of a registration statement filed with the SEC by us
and the trusts. The full registration statement can be obtained from the SEC as
indicated above, or from us.
 
    The SEC allows UnionBanCal Corporation to "incorporate by reference" the
information we file with the SEC. This permits us to disclose important
information to you by referring to these filed documents. Any information
referred to in this way is considered part of this prospectus, and any
information filed
 
                                       2
<PAGE>
with the SEC by us after the date of this prospectus will automatically be
deemed to update and supersede this information. We incorporate by reference the
following documents that have been filed with the SEC:
 
    - Annual Report on Form 10-K for the year ended December 31, 1997 and all
      amendments thereto;
 
    - Quarterly Reports on Form 10-Q for the quarters ended March 31, 1998, June
      30, 1998 and September 30, 1998 and all amendments thereto;
 
    - Current Report on Form 8-K dated August 10, 1998.
 
    UnionBanCal Corporation also incorporates by reference any future filings
made with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange
Act of 1934 (the "Exchange Act") until we file a post-effective amendment which
indicates the termination of the offering of the securities made by this
prospectus.
 
    We will provide without charge upon written or oral request a copy of any or
all of the documents that are incorporated by reference into this prospectus,
other than exhibits which are specifically incorporated by reference into such
documents. Requests should be directed to Investor Relations, UnionBanCal
Corporation, 400 California Street, San Francisco, California 94104 (telephone
415-765-2969).
 
    There are no separate financial statements of the trusts in this prospectus.
We do not believe such financial statements would be helpful because:
 
    - The trusts are subsidiaries of UnionBanCal Corporation, which files
      consolidated financial information under the Exchange Act.
 
    - The trusts do not have any independent operations other than issuing the
      preferred and common securities and purchasing the Debt Securities of
      UnionBanCal Corporation.
 
    - The trust's only material assets will be the debt securities of
      UnionBanCal Corporation when issued.
 
    - The combined obligations of UnionBanCal Corporation under the debt
      securities, the Trust Preferred Securities Guarantees, the Declarations
      and the Indenture (each as defined herein) have the effect of providing a
      full, irrevocable and unconditional guarantee of the trusts' obligations
      under their trust preferred securities. See "Description of Debt
      Securities," "Description of the Trust Preferred Securities Guarantees"
      and "Relationship Among the Trust Preferred Securities, the Trust
      Preferred Securities Guarantee and the Debt Securities Held by Each
      Trust."
 
               SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS
 
    This prospectus or the information incorporated by reference herein includes
forward-looking statements within the meaning of Section 27A of the Securities
Act of 1933, as amended (the "Securities Act") and Section 21E of the Exchange
Act. Some of the forward-looking statements can be identified by the use of
forward-looking words such as "believes," "expects," "may," "will," "should,"
"seeks," "approximately," "intends," "plans," "estimates," or "anticipates" or
the negative of those words or other comparable terminology. Forward-looking
statements involve inherent risks and uncertainties. A number of important
factors could cause actual results to differ materially from those in the
forward-looking statements. Some factors include fluctuations in interest rates,
inflation, government regulations, and economic conditions and competition in
the geographic and business areas in which we conduct our operations. For a
discussion of factors that could cause actual results to differ, please see the
discussion under "Risk Factors" contained in this prospectus generally, in any
prospectus supplement related hereto, and in other information contained in our
publicly available SEC filings and press releases.
 
                                       3
<PAGE>
                                  THE COMPANY
 
    UnionBanCal Corporation, or "UNBC," is the third largest commercial bank in
California, based on both total assets and total deposits in California, and
among the 30 largest in the United States. Having roots as far back as 1864, we
are among the oldest banks on the West Coast. At September 30, 1998, we had 244
full-service branches in California, 6 full-service branches in Oregon and
Washington, 2 facilities in Texas and New York and 18 offices abroad. Our bank
was formed through the combination of Union Bank and BanCal Tri-State
Corporation in 1996. We are presently approximately 82% owned by The Bank of
Tokyo-Mitsubishi, Ltd., or "BTM."
 
    We provide a wide range of financial services to retail customers, small
businesses, middle-market companies and major corporations. These services
include a variety of personal and commercial financial products, including
consumer and small-business lending, corporate and international lending and
cash management, treasury, trust and investment advisory services. Most of our
customers are located in California, the nation's most populous state with over
32 million residents.
 
    As of September 30, 1998, our total assets were $31.4 billion, total
deposits were $23.7 billion and total shareholders' equity was $3.0 billion. Our
net income for the nine months ended September 30, 1998 was $352.4 million, and
net income per diluted share was $6.02 ($2.01 after giving effect to the 3-for-1
stock split described below).
 
THE STRATEGIC REPOSITIONING
 
    THE TRANSACTIONS.  On November 19, 1998, BTM and UNBC announced the proposed
public offering of $750 million of UNBC common stock, all of which is owned by
BTM ("the Common Stock Offering"). At the same time, we announced that we will
seek to repurchase up to $500 million of UNBC common stock. It is expected that
we will repurchase $250 million of UNBC common stock from BTM concurrently with
the closing of the Common Stock Offering by BTM. We may also repurchase up to an
additional $250 million of UNBC common stock from other foreign institutional
shareholders. To finance the repurchases, we announced a proposed public
offering of trust preferred securities (the "Trust Preferred Offering"). The
size of the Trust Preferred Offering will depend upon the amount of UNBC common
stock to be repurchased. The Trust Preferred Offering, the Common Stock Offering
and the repurchases are referred to as the "Transactions." We anticipate that
the Common Stock Offering and the Trust Preferred Offering will close in the
first quarter of 1999, with the repurchase of common stock from BTM completed
concurrently with the closing of the Common Stock Offering.
 
    The Transactions are principally designed to improve our return on average
common equity and earnings per share and increase our public float.
 
    - The repurchase of the common stock from BTM, the issuance of the trust
      preferred securities and the increase of the common stock dividend
      (described below) would, on a pro forma basis:
 
       - increase UNBC's return on average common equity from    % to    % at
         September 30, 1998; and
 
       - increase UNBC's earnings per share for the nine months ended September
         30, 1998 and the year ended December 31, 1997, from $   up to $   and
         from $   up to $   , respectively (representing an approximate        %
         increase and    % increase, respectively).
 
    - The sale of the common stock by BTM to the public will also substantially
      increase the percentage of UNBC's common stock that is held by public
      investors (its "public float"), thereby increasing the stock's liquidity.
 
                                       4
<PAGE>
    In addition, we believe the Transactions will provide UNBC with additional
benefits, including increased market visibility as a result of more research
coverage and a more attractive acquisition currency, both resulting from an
increased public float.
 
    DIVIDEND POLICY AND STOCK SPLIT.  On November 19, 1998, we announced a 36%
increase in our quarterly common stock dividend, from $.42 per share to $.57 per
share, to be paid on January 8, 1999 to shareholders of record as of December 4,
1998. In addition, we announced a 3-for-1 stock split payable to shareholders of
record on December 7, 1998, with shares issuable on December 21, 1998. After
giving effect to the stock split, our quarterly common stock dividend will be
$0.19 per share.
 
THE BANK OF TOKYO-MITSUBISHI, LTD.
 
    The Bank of Tokyo-Mitsubishi, Ltd. is Japan's largest bank, based on total
assets, with a domestic network that comprises approximately 350 branches,
sub-branches and agencies and an overseas network that includes more than 400
facilities located in all the major financial and commercial centers of the
world. BTM offers an extensive scope of financial products and services to
businesses, governments and private individuals.
 
    UNBC is BTM's largest overseas subsidiary. BTM was created through the
merger, on April 1, 1996, of The Bank of Tokyo, Ltd. and The Mitsubishi Bank,
Limited. In connection with that merger, Union Bank (formerly majority owned by
The Bank of Tokyo) and BanCal Tri-State Corporation (formerly wholly owned by
Mitsubishi Bank) combined on April 1, 1996. As a result, BTM came to own over
80% of UNBC. BTM has stated that it intends to maintain its majority stake in
UNBC after the closing of the Transactions.
 
BANKING SERVICES
 
    UNBC's operations are divided into five primary segments: the Community
Banking Group; the Commercial Financial Services Group; the Trust and Private
Financial Services Group; the Global Markets Group; and the International
Banking Group.
 
    The Community Banking Group offers a comprehensive line of loan and deposit
products for consumers and businesses primarily located in California. It
provides services through its 244 branches in California, as well as branches in
Oregon and Washington. In addition to traditional consumer and business loan
products, the Community Banking Group offers credit products to small to
mid-size agricultural enterprises, international trade and settlement services,
and E-banking through our web site and through personal financial management
products. Average assets in this group for the nine months ended September 30,
1998 were $10.3 billion of our total assets.
 
    The Commercial Financial Services Group offers a full line of commercial
financial services to California middle market companies, large corporations
across the nation, real estate companies and other, more specialized industries
such as oil and gas, and energy utilities, media, communications, healthcare,
forest products, finance and retailing. Through its relationships with title and
escrow companies, government agencies and other primarily corporate customers
who provide large pools of deposits, this group provides a significant source of
funding for UNBC. Average assets in the Commercial Financial Services Group for
the nine months ended September 30, 1998 were $11.7 billion of our total assets.
 
    The Trust and Private Financial Services Group, through its five main
business divisions, offers trust, custody and advisory services to institutional
and individual customers. Within these divisions, this group provides trust and
private banking services to high net worth individuals, and it provides
investment management and advisory services to trust customers, to our
proprietary mutual fund family, HighMark, and to traditional employee benefit
and 401(k) plans. This group also provides global and domestic custody,
securities lending and corporate trust services. Through our registered
broker/dealer, the Trust and Private Financal Services Group provides brokerage
services to trust and retail customers. At September 30, 1998, this group had
approximately $90 billion in assets under administration.
 
                                       5
<PAGE>
    The Global Markets Group offers customers a broad range of risk management
products such as foreign exchange, interest rate swaps, caps and floors. It
manages the market-related risks for UNBC as part of its responsibilities for
asset/liability management. This group also originates debt instruments for bank
eligible issuers and trades debt instruments in the secondary market. Average
assets in the Global Markets Group for the nine months ended September 30, 1998
were $4.3 billion of our total assets.
 
    The International Banking Group offers corporate banking products through
its full service foreign branches in Tokyo, Taipei, and Seoul and its banking
units and representative offices in other parts of Asia and Latin America. A
leader in international correspondent banking, this group ranks among the top 5
U.S. banks doing correspondent banking in Asia. Through its branches in the
United States, the International Banking Group also provides trade finance and
other international services for export/import activity. Average assets in this
group for the nine months ended September 30, 1998 were $3.0 billion of our
total assets.
 
OPERATING STRATEGY
 
    Our operating strategy is focused on the following:
 
    - CAPITALIZE ON STRONG POSITION IN CORE CALIFORNIA MARKET. We believe that
      one of our primary strategic strengths is our established position in the
      attractive California bank market. California is the largest state in the
      U.S., with over 32 million residents and nearly $1 trillion in gross state
      product. Based on both total assets and total deposits in California, we
      are the third largest commercial bank in California and we are among the
      oldest banks on the West Coast. Based on total deposits, we also hold the
      number three commercial bank positions in Los Angeles, San Francisco and
      San Diego. We serve approximately one million households and small
      businesses, with 244 banking offices in California. We also offer a
      distinctive combination of traditional community bank service with a large
      branch network and a broad array of products. We intend to continue to
      capitalize on the high quality of our customer service, taking advantage
      of any changes in service levels caused by recent increases in bank merger
      activity in the California market.
 
    - FOCUS ON UNDERSERVED, PROFITABLE BUSINESS NICHES. In recent years, we have
      increased our strategic focus on products and markets that are more
      specialized and, in many cases, more profitable than those typically
      serviced by the larger "Super-regional banks" or "Mega-banks." These niche
      products and markets include specialized lending, trade finance, private
      client services and asset management. In specialized lending, we focus on
      middle market clients in industries such as communications and media, oil
      and gas and utilities. We seek to provide highly responsive customer
      service, along with our broad industry experience, to create and maintain
      long-term relationships with clients who are often underserved by larger
      banks. Trade finance is attactive to us because it is typically a
      fee-based recurring revenue stream which possesses relatively low credit
      risk characteristics. In addition, we are increasing our focus on other,
      more fee-based businesses, such as private client services and asset
      management. We intend to offer our HighMark family of funds in Japan,
      building upon our relationship with BTM to expand our asset management
      business into international markets. Our non-interest income (net of gain
      on the sale of credit card portfolio) has increased from 26% of total
      revenue in 1995 to 28% of total revenue for the nine month period ended
      September 30, 1998. For the nine month period ended September 30, 1997 to
      the nine month period ended September 30, 1998, non-interest income (net
      of gain on the sale of credit card portfolio) increased from $342.6
      million to $382.9 million.
 
    - MAINTAIN HIGH LENDING STANDARDS AND STRONG ASSET QUALITY PROFILE. We
      strive to maintain strong asset quality through our underwriting
      standards, credit policies and ongoing credit reviews of our existing loan
      portfolio. These criteria along with the recent strength of the California
      economy have resulted in our current high quality loan portfolio. For the
      nine months ended September 30, 1998, our ratio of net loans charged off
      to average total loans was 0.12%, or the third lowest of the 30
 
                                       6
<PAGE>
      largest commercial banks in the United States. At September 30, 1998, our
      ratio of non-performing assets to total assets was 0.26%, or the seventh
      lowest of the 30 largest commercial banks in the United States. In
      addition, as of September 30, 1998, our ratio of reserves to total loans
      was 2.02%, or the eighth highest of the 30 largest commercial banks in the
      United States. At September 30, 1998, no industry concentration exceeded
      10% of our total commercial, financial and industrial loans. Additionally,
      at September 30, 1998, we had a limited number of borrowers with larger
      loans, with 10 borrowers who had total outstanding balances of over $50
      million, and only one borrower who had a total outstanding balance of over
      $75 million.
 
    - IDENTIFY STRATEGIC BUSINESSES AND CONSIDER POTENTIAL ACQUISITIONS OR
      DIVESTITURES. We view selective acquisitions and divestitures, as well as
      internal growth, as the primary means to grow and enhance our core
      businesses. We will consider acquisitions of banks and other financial
      services businesses that will increase our presence in existing markets or
      allow us to expand into contiguous markets. We will also consider
      acquisitions in other complementary financial services businesses in which
      we believe there exists superior growth potential. In addition, we will
      consider exiting businesses which we believe are not strategic and do not
      meet our core business criteria. Our strategic business evaluation process
      focuses on historical financial performance, the competitive environment
      and future growth potential.
 
                                       7
<PAGE>
                                   THE TRUSTS
 
    UNBC created four Delaware business trusts pursuant to four Declarations of
Trust executed by us as sponsor for each trust and five appointed trustees for
each trust. The trusts are named UnionBanCal Finance Trust I, UnionBanCal
Finance Trust II, UnionBanCal Finance Trust III, and UnionBanCal Finance Trust
IV (each a "Trust"). Prior to the issuance of trust preferred securities, we
will file an Amended and Restated Declaration of Trust (a "Declaration") for
each Trust, which will state the terms and conditions for each Trust to issue
and sell its preferred securities and common securities. A form of Declaration
is filed as an exhibit to the registration statement of which this prospectus is
a part.
 
    Each Trust will exist solely to:
 
    - issue and sell its preferred and common securities;
 
    - use the proceeds from the sale of its preferred and common securities to
      purchase a series of UNBC's debt securities; and
 
    - engage in other activities that are necessary or incidental to these
      purposes.
 
    We will purchase all of the common securities of each Trust. Unless
otherwise stated in the applicable prospectus supplement, the trust common
securities will represent an aggregate liquidation amount equal to at least 3%
of each Trust's total capitalization. The trust preferred securities will
represent the remaining approximately 97% of such Trust's total capitalization.
The trust common securities will have terms substantially identical to, and will
rank equal in priority of payment with, the trust preferred securities. However,
if an event of default under the related Declaration has occurred, then cash
distributions and liquidation, redemption and other amounts payable on the trust
common securities will be subordinate to the trust preferred securities in
priority of payment.
 
    The trust preferred securities will be guaranteed by UNBC as described later
in this prospectus and the applicable prospectus supplement.
 
    We have appointed five trustees to conduct the Trusts' business and affairs:
 
    - The First National Bank of Chicago ("Property Trustee")
 
    - First Chicago Delaware Inc. ("Delaware Trustee")
 
    - Three officers of UNBC ("Regular Trustees")
 
    Only UNBC, as owner of the common securities of each Trust, can remove or
replace the trustees. In addition, we can increase or decrease the number of
trustees. The majority of trustees, however, will always be Regular Trustees.
 
    UNBC will pay all fees and expenses related to each Trust and each offering
of the related preferred securities and will pay all ongoing costs and expenses
of each Trust, except each Trust's obligations under the related preferred and
common securities.
 
    The Trusts will not have separate financial statements. The statements would
not be material to holders of the preferred securities because the Trusts will
not have any independent operations. The Trusts exist solely for the reasons
summarized above.
 
                                       8
<PAGE>
                                  RISK FACTORS
 
    YOU SHOULD CAREFULLY CONSIDER THE FOLLOWING RISKS AS WELL AS THE OTHER
INFORMATION CONTAINED OR INCORPORATED BY REFERENCE IN THIS PROSPECTUS BEFORE
PURCHASING THE SECURITIES.
 
CALIFORNIA ECONOMIC CONDITIONS
 
    A substantial majority of our assets and deposits are generated in
California. As a result, poor economic conditions in California may cause us to
incur losses associated with higher default rates and decreased collateral
values in our loan portfolio. In the early 1990s, the California economy
experienced an economic recession that resulted in increases in the level of
delinquencies and losses for us and many of the state's financial institutions.
If California were to experience another recession, it is expected that our
level of problem assets would increase accordingly. The current economic crisis
in Asia is expected to continue to negatively impact the economic conditions in
California.
 
    We are also subject to certain industry-specific economic factors. For
example, a portion of our total loan portfolio is related to real estate
obligations, and a portion of our recent growth has been fueled by the general
real estate recovery in California. Accordingly, a downturn in the real estate
industry in California could have an adverse effect on our operations.
Similarly, a portion of our total loan portfolio is to borrowers in the
agricultural industry. Last year's weather effects of "El Nino," combined with
low commodity prices, may adversely affect the agricultural industry and,
consequently, may impact our business negatively.
 
INTEREST RATE RISK
 
    Significant increases in market interest rates, or the perception that an
increase may occur, could adversely affect both our ability to originate new
loans and our ability to grow. Conversely, a decrease in interest rates could
result in an acceleration in the prepayment of loans. In addition, changes in
market interest rates or in the relationships between short-term and long-term
market interest rates or between different interest rate indices (i.e., basis
risk) could affect the interest rates charged on interest-earning assets
differently than the interest rates paid on interest-bearing liabilities. This
could result in an increase in interest expense relative to interest income. An
increase in market interest rates also could adversely affect the ability of our
floating-rate borrowers to meet their higher payment obligations, which could
result in an increase in non-performing assets and net-loan losses.
 
FAILURE TO CONSUMMATE TRANSACTIONS
 
    Although UNBC and BTM intend to consummate the Transactions during the first
quarter of 1999, the Transactions may not occur. The repurchases from BTM and
the other foreign institutional holders will be conditioned on the closing of
the Common Stock Offering and the Trust Preferred Offering. In addition, the
Common Stock Offering is conditioned on the closing of the repurchase from BTM.
Accordingly, if BTM does not complete the Common Stock Offering, the repurchases
will not occur. If any of the Transactions does not occur, we may not recognize
any of the anticipated benefits, including the expected increase in the
liquidity of our common stock, earnings per share and return on average common
equity. In addition, we do not know if we will be able to successfully complete
the repurchase of any shares from the other foreign institutional holders.
 
CONTROL BY AND RELATIONSHIP WITH THE BANK OF TOKYO-MITSUBISHI, LTD.; CONFLICTS
  OF INTEREST
 
    Upon completion of the Common Stock Offering and the repurchases, BTM will
continue to own a majority of the outstanding shares of our common stock. BTM
will continue to be able to elect all of our directors and to control the vote
on all matters, including determinations such as:
 
    - approval of mergers or other business combinations;
 
                                       9
<PAGE>
    - sales of all or substantially all of UNBC's assets;
 
    - any matters submitted to a vote of UNBC's shareholders;
 
    - issuance of any additional common stock or other equity securities;
 
    - incurrence of debt other than in the ordinary course of business;
 
    - the selection and tenure of the Chief Executive Officer of UNBC;
 
    - payment of dividends with respect to common stock or other equity
      securities; and
 
    - matters that might be favorable to BTM.
 
    BTM's ability to prevent an unsolicited bid for UNBC or any other change in
control could have an adverse effect on the market price for our common stock
and other UNBC securities. In addition, although we fund our operations
independently of BTM and believe our business is not necessarily closely related
to the business of, and the outlook for, BTM, BTM's credit ratings may affect
our credit ratings. BTM's credit ratings were downgraded in October 1998 by
Standard and Poor's Corporation and its credit ratings currently are on Moody's
Investors Service, Inc.'s credit watch with negative implications. Any future
downgrading of BTM's credit rating could adversely affect our credit ratings.
Therefore, as long as BTM maintains a majority interest in UNBC, a deterioration
in BTM's financial condition could result in an increase in our borrowing costs
and could impair our access to the public and private capital markets. BTM is
also subject to regulatory oversight and review. Our business operations and
expansion plans could be negatively affected by regulatory concerns related to
the Japanese financial system and BTM.
 
    As part of BTM's normal risk management processes, BTM manages its global
credit exposures and concentrations on an aggregate basis, including UNBC.
Therefore, at certain levels, our ability to approve certain credits and
categories of customers is subject to concurrence by BTM.
 
    BTM and UNBC may wish to extend credit to the same customer. Our ability to
do so may be limited for various reasons, including BTM's aggregate credit
exposure and marketing policies.
 
    A majority of UNBC's directors are not officers or employees of UNBC or any
of its affiliates, including BTM ("Outside Directors"). However, BTM could
change the composition of our Board of Directors so that it would not have a
majority of Outside Directors. Our directors' and officers' ownership interests
in BTM's common stock or service as a director or officer or other employee of
both UNBC and BTM could create or appear to create potential conflicts of
interest, especially since UNBC and BTM both compete in the United States
banking industry.
 
COMPETITION
 
    Banking is a highly competitive business. We compete actively for loan,
deposit, and other financial services business in California, as well as
nationally and internationally. Our competitors include a large number of state
and national banks, thrift institutions and major foreign-affiliated or foreign
banks, as well as many financial and nonfinancial firms that offer services
similar to those offered by us or our subsidiaries. Some of our competitors are
community banks that have strong local market positions, and some are large
financial institutions (such as Bank of America, Wells Fargo and Washington
Mutual) that have substantial capital, technology and marketing resources. Such
large financial institutions may have greater access to capital at a lower cost
than UNBC, which may adversely affect our ability to compete effectively.
 
    In addition, there have been a number of recent mergers involving financial
institutions located in California. Some of the merged banks, such as Wells
Fargo/Norwest, employ a strong community-based banking model of doing business
that may increase the competition with our distinctive combination of
traditional community bank service coupled with a large branch network.
 
                                       10
<PAGE>
HOLDING COMPANY STRUCTURE
 
    A substantial portion of our cash flow typically comes from dividends paid
to us by our bank and nonbank subsidiaries. Various statutory provisions
restrict the amount of dividends our subsidiaries can pay to us without
regulatory approval. In addition, because we are a holding company, our rights
and the rights of our creditors and shareholders, including the holders of our
securities, to participate in the assets of any subsidiary upon its liquidation
or recapitalization will be subject to claims of the subsidiary's creditors,
except to the extent that we may be a creditor of the applicable subsidiary with
recognized claims against it.
 
REGULATION
 
    We are subject to significant federal and state regulation and supervision,
which is primarily for the benefit and protection of our customers and not for
the benefit of investors. In the past, our business has been materially affected
by these regulations. This trend is likely to continue in the future. Laws,
regulations or policies currently affecting us and our subsidiaries may change
at any time. Regulatory authorities may also change their interpretation of
these statutes and regulations. Therefore, our business may be adversely
affected by any future changes in laws, regulations, policies or
interpretations.
 
    Additionally, our international activities may be subject to the laws and
regulations of the jurisdiction where business is being conducted. International
laws, regulations and policies affecting us and our subsidiaries may change at
any time and affect our business opportunities and competitiveness in these
jurisdictions. Due to BTM's controlling ownership of UNBC, laws, regulations and
policies adopted or enforced by the Government of Japan may adversely affect our
activities and investments and those of our subsidiaries in the future.
 
    Under long-standing policy of the Board of Governors of the Federal Reserve
System, a bank holding company is expected to act as a source of financial
strength for its subsidiary banks. As a result of that policy, UNBC may be
required to commit financial and other resources to its subsidiary bank in
circumstances where it might not otherwise do so.
 
COMPUTER TECHNOLOGIES
 
    The year 2000 problem results from an inability of computer systems to
accurately recognize dates on and after the year 2000. The year 2000 problem is
a broad business issue that extends beyond computer failures to possible
failures of entire infrastructures, such as telecommunications and data
networks, building facilities and security systems and systems of other
institutions, including governmental agencies, to settle transactions.
 
    Many of our critical operations are not presently ready to operate normally
in the year 2000 and beyond, although preparations are underway to correct this.
We are preparing for the century change with an enterprise-wide year 2000
program. It has identified all of the major application and processing systems,
and sought external and internal resources to replace and test the systems.
Purchased software, internally developed systems and systems supported by
external parties are being tested as part of the program. Customers and vendors
that have significant relationships with UNBC are being evaluated to determine
whether they are adequately preparing for the year 2000. In addition,
contingency plans are being developed to reduce the impact of some potential
events that may occur. However, there can be no guarantee that the systems of
vendors or customers with which we do business will be completed on a timely
basis, or that contingency plans will shield operations from failures that may
occur.
 
    The year 2000 problem poses the following principal risks to our business:
 
    - disruption of our business due to our failure to achieve year 2000
      readiness;
 
    - disruption of our business due to failure of third parties to achieve year
      2000 readiness; and
 
                                       11
<PAGE>
    - disruption in our funding and repayment operations due to failure of fund
      providers and obligors to achieve year 2000 readiness.
 
    The total cost of the year 2000 project is estimated to be approximately $50
million. The cost of the year 2000 project is being funded by normal operating
cash flow and staffed by external resources as well as internal staff
re-deployed from less time-sensitive assignments. Estimated total cost could
change further as analysis continues. Because of the range of possible issues
and the large number of variables involved, however, we cannot definitively
quantify the potential costs. For example, our remediation efforts or the
efforts of third parties may be unsuccessful. Any failure of such remediation
efforts could result in a loss of business, damage to our reputation or legal
liability. Consequently, such failures could have a material adverse effect on
our business.
 
POSSIBLE FUTURE SALES OF SHARES BY THE BANK OF TOKYO-MITSUBISHI, LTD.
 
    Although The Bank of Tokyo-Mitsubishi, Ltd. has announced its intention to
maintain its majority ownership in UNBC, it will be free to sell shares of our
common stock after the completion of the Common Stock Offering and the
repurchase of UNBC common stock from BTM, subject to applicable federal
securities law and the restrictions discussed below. By virtue of its current
control of UNBC, BTM could sell large amounts of its shares of our common stock
by causing us to file a registration statement with respect to such stock. In
addition, BTM could sell its shares of our common stock without registration
pursuant to Rule 144 under the Securities Act. Although we can make no
prediction as to the effect, if any, that such sales would have on the market
price prevailing from time to time, sales of substantial amounts of our common
stock, or the perception that such sales could occur, could adversely affect
prevailing market prices. If BTM sells or transfers its shares of our common
stock as a block, another person or entity could become the controlling
shareholder of UNBC.
 
                                USE OF PROCEEDS
 
    The net proceeds of the sale of the common and preferred securities issued
by each Trust will be invested by such Trust in the related series of debt
securities of the Company. Unless otherwise stated in the applicable prospectus
supplement, the Company intends to use such proceeds, in addition to the net
proceeds of any securities sold by the Company, for possible repurchases of the
Company's outstanding securities and for general corporate purposes, including
working capital, acquisitions and other business opportunities.
 
                                       12
<PAGE>
                RATIO OF EARNINGS TO COMBINED FIXED CHARGES AND
                           PREFERRED STOCK DIVIDENDS
 
    The following table sets forth the ratio of earnings to combined fixed
charges and preferred stock dividends for the Company.
 
<TABLE>
<CAPTION>
                                                                                                              NINE MONTHS ENDED
                                                                    YEARS ENDED DECEMBER 31,                    SEPTEMBER 30,
                                                      -----------------------------------------------------  --------------------
                                                        1993       1994       1995       1996       1997       1997       1998
                                                      ---------  ---------  ---------  ---------  ---------  ---------  ---------
<S>                                                   <C>        <C>        <C>        <C>        <C>        <C>        <C>
Ratio of earnings to combined fixed charges and
  preferred stock dividends:
    Excluding interest on deposits..................       1.33x      1.46x      1.68x      1.51x      1.78x      1.79x      1.85x
    Including interest on deposits..................       1.20       1.29       1.42       1.30       1.45       1.46       1.49
</TABLE>
 
    For purposes of computing these ratios, earnings represent consolidated
income before income taxes and cumulative effects of accounting changes plus
consolidated fixed charges. Consolidated fixed charges represent interest
expense, including interest on deposits where indicated, and such portion of
rental expense deemed representative of the interest factor. The denominator is
increased for preferred stock dividend requirements which represent the amount
of pre-tax earnings required to cover such dividend requirements.
 
                           DESCRIPTION OF SECURITIES
 
    This prospectus contains a summary of our common stock, preferred stock,
depositary shares, debt securities, preferred securities of the Trusts, and
preferred securities guarantees of UNBC relating to each Trust. The securities
issued by the Trusts will be identical with respect to each Trust, except as
otherwise described in the prospectus supplement for such securities. These
summaries are not meant to be a complete description of each security. However,
this prospectus and the accompanying prospectus supplement contain the material
terms and conditions for each security.
 
DESCRIPTION OF CAPITAL STOCK
 
    The following descriptions of the capital stock of UNBC do not purport to be
complete and are subject to and qualified in their entirety by reference to our
Amended and Restated Articles of Incorporation (the "Articles of
Incorporation"), our ByLaws (the "Bylaws") and the California General
Corporation Law ("CGCL"). We have filed copies of the Articles of Incorporation
and the Bylaws with the SEC and such documents are incorporated by reference
into the Registration Statement of which this prospectus is a part.
 
    UNBC's authorized capital stock consists of 105,000,000 shares, of which
100,000,000 shares are common stock and 5,000,000 shares are preferred stock. As
of October 31, 1998, 58,403,188 shares of our common stock were issued and
outstanding, and no shares of our preferred stock were issued or outstanding. On
November 18, 1998, our Board of Directors approved a 3-for-1 common stock split
payable to stockholders of record on December 7, 1998, with shares issuable on
December 21, 1998, and a corresponding increase in the number of authorized
shares of our common stock to 300,000,000.
 
COMMON STOCK
 
    Each holder of our common stock is entitled to one vote for each share held
on all matters to be voted upon by our shareholders. The holders of outstanding
shares of our common stock, subject to any preferences that may be applicable to
any outstanding series of our preferred stock, are entitled to receive ratably
such dividends out of assets legally available therefor at such times and in
such amounts as our Board of Directors may from time to time determine. Upon
liquidation or dissolution of UNBC, the
 
                                       13
<PAGE>
holders of our common stock will be entitled to share ratably in the assets of
UNBC legally available for distribution to shareholders after payment of
liabilities and subject to the prior rights of any holders of any of our
preferred stock then outstanding. Holders of our common stock have no
conversion, sinking fund, redemption, preemptive or subscription rights. In
addition, our common stock does not have cumulative voting rights. Shares of our
common stock are not subject to further calls or assessments by UNBC.
 
PREFERRED STOCK
 
    We are authorized to issue 5,000,000 shares of preferred stock, none of
which currently is issued or outstanding. Our Board has the authority, without
further action by the shareholders, to determine and alter the rights,
preferences, privileges and restrictions granted to or imposed upon any wholly
unissued series of our preferred stock and to fix the number of shares, dividend
rights, conversion or exchange rights, voting rights, redemption rights,
liquidation preferences, and sinking funds of any series of our preferred stock.
The holders of our preferred stock will have the right to vote separately as a
class on any proposal involving fundamental changes in the rights of holders of
such preferred stock pursuant to the CGCL.
 
    The terms on which our preferred stock may be convertible into or
exchangeable for our common stock or other securities of UNBC will be set forth
in the prospectus supplement relating thereto. Such terms will include
provisions as to whether conversion or exchange is mandatory, at the option of
the holder, or at the option of UNBC, and may include provisions pursuant to
which the number of shares of our common stock or other securities of UNBC to be
received by the holders of Preferred Stock would be subject to adjustment.
 
CERTAIN PROVISIONS OF THE ARTICLES OF INCORPORATION, BYLAWS AND CGCL
 
    PREFERRED STOCK.  Under the Articles of Incorporation, our Board may provide
by resolution for the issuance of shares of one or more series of our preferred
stock and may fix the terms and conditions of each such series. The authorized
shares of our preferred stock will be available for issuance without further
action by our shareholders, unless shareholder action is required by applicable
law or by the rules of a stock exchange on which any series of UNBC's stock may
be listed.
 
    This gives our Board the power to approve the issuance of a series of
preferred stock of UNBC that could, depending on its terms, either impede or
facilitate the completion of a merger, tender offer or other takeover attempt.
For example, the issuance of new shares might impede a business combination if
the terms of those shares include voting rights which would enable a holder to
block business combinations. Conversely, the issuance of new shares might
facilitate a business combination if those shares have general voting rights
sufficient to satisfy an applicable percentage vote requirement.
 
    WRITTEN CONSENTS.  Bylaws provide that any shareholder action can be taken
by written consent of the shareholders. As a result, BTM, which owns a majority
of shares of our common stock, can take action by written consent.
 
    DIRECTORS' LIABILITY.  The Articles of Incorporation provide for
indemnification of directors to the fullest extent authorized by California law.
Section 317 of the CGCL contains provisions permitting, and in some situations,
requiring California corporations to provide indemnification to their directors
and officers for losses and litigation expenses incurred in connection with
their service to the corporation in those capacities.
 
TRANSFER AGENT AND REGISTRAR
 
    Harris Trust Company of California acts as transfer agent and registrar for
our common stock.
 
                                       14
<PAGE>
DESCRIPTION OF DEPOSITARY SHARES
 
    The following description of the depositary shares does not purport to be
complete and is subject to and qualified in its entirety by the Deposit
Agreement (as defined herein) and the depositary receipt relating to the
preferred stock which is attached to the Deposit Agreement. Such documents will
be filed with the SEC as an exhibit to the registration statement of which this
prospectus is a part.
 
    If we elect to offer fractional interests in shares of preferred stock, we
will provide for the issuance by a depositary to the public of receipts for
depositary shares, each of which will represent fractional interests of
preferred stock. The shares of preferred stock underlying the depositary shares
will be deposited under a Deposit Agreement (the "Deposit Agreement") between us
and a bank or trust company selected by us having its principal office in the
United States and having a combined capital and surplus of at least $50 million.
The depositary shares will be evidenced by depositary receipts issued under the
Deposit Agreement.
 
    Subject to the terms of the Deposit Agreement, each owner of depositary
shares will be entitled, in proportion to the applicable fractional interests in
shares of preferred stock underlying such depositary shares, to all the rights
and preferences of the preferred stock underlying such depositary shares.
Individuals purchasing the fractional interests in shares of the related
preferred stock will receive depositary receipts according to the terms of the
offering described in the prospectus supplement.
 
    The depositary will distribute all cash dividends or other cash
distributions received for the preferred stock to the entitled record holders of
depositary shares representing such preferred stock in proportion to the number
of depositary shares owned by such holders on the relevant record date. The
depositary will distribute only such amount that can be distributed without
attributing to any holder of depositary shares a fraction of one cent. The
balance not distributed will be added to and treated as part of the next sum
received by the depositary for distribution to record holders of depositary
shares.
 
    If there is a distribution other than in cash, the depositary will
distribute property received by it to the entitled record holders of depositary
shares, in proportion, insofar as possible, to the number of depositary shares
owned by such holders, unless the depositary determines (after consultation with
us) that it is not feasible to make such distribution. If this occurs, the
depositary may, with our approval, sell such property and distribute the net
proceeds from such sale to such holders. The Deposit Agreement also will contain
provisions relating to how any subscription or similar rights offered by us to
holders of the preferred stock will be available to the holders of the
depositary shares.
 
    If any series of preferred stock underlying the depositary shares is subject
to conversion or exchange, each record holder of depositary receipts will have
the right or obligation to convert or exchange the depositary shares represented
by such depositary receipts.
 
    If a series of the preferred stock underlying the depositary shares is
subject to redemption, the depositary shares will be redeemed from the proceeds
received by the depositary resulting from the redemption, in whole or in part,
of such series of the preferred stock held by the depositary. The depositary
will mail notice of redemption not less than 30 and not more than 60 days prior
to the date fixed for redemption to the record holders of the depositary shares
to be so redeemed at their addresses appearing in the depositary's books. The
redemption price per depositary share will be equal to the applicable fraction
of the redemption price per share payable on such series of the preferred stock.
Whenever we redeem shares of preferred stock held by the depositary, the
depositary will redeem as of the same redemption date, the number of depositary
shares representing the preferred stock. If less than all the depositary shares
are to be redeemed, the depositary shares to be redeemed will be selected by
lot, PRO RATA or such other method as is determined by the depositary.
 
    After the date fixed for redemption, the depositary shares called for
redemption will no longer be outstanding. When the depositary shares are no
longer outstanding, all rights of the holders will cease, except the right to
receive money, securities or other property payable upon such redemption and any
 
                                       15
<PAGE>
money, securities or other property that the holders of such depositary shares
were entitled to upon such redemption upon the surrender to the depositary of
the depositary receipts evidencing such depositary shares.
 
    Upon receipt of notice of any meeting at which the holders of the preferred
stock are entitled to vote, the depositary will mail the particulars of such
meeting to the record holders of the depositary shares representing such
preferred stock. Each record holder of such depositary shares on the record date
(which will be the same date as the record date for the preferred stock) will be
entitled to instruct the depositary on the exercise of the voting rights
representing the shares of preferred stock underlying such holder's depositary
shares. The depositary will try, if practical, to vote the number of shares of
preferred stock underlying such depositary shares according to such
instructions, and we will agree to take all reasonable action requested by the
depositary in order to enable the depositary to do so.
 
    The form of depositary receipt evidencing the depositary shares and any
provision of the Deposit Agreement may be amended by agreement between us and
the depositary. Any amendment, however, that materially and adversely alters the
rights of the existing holders of depositary shares will not be effective unless
approved by the record holders of at least a majority of the depositary shares
then outstanding. A Deposit Agreement may be terminated by us or the depositary
only if (i) all related outstanding depositary shares have been redeemed or (ii)
there has been a final distribution of the preferred stock of the relevant
series in connection with our liquidation, dissolution or winding up and such
distribution has been distributed to the holders of the related depositary
shares.
 
    We will pay all transfer and other taxes and governmental charges arising
solely from the existence of the depositary arrangements. We will pay associated
charges of the depositary for the initial deposit of the preferred stock and any
redemption of the preferred stock. Holders of depositary shares will pay
transfer and other taxes and governmental charges and such other charges as are
stated in the Deposit Agreement for their accounts.
 
    The depositary may resign by delivering notice to us, and we may remove the
depositary. Resignations or removals will take effect upon the appointment of a
successor depositary and its acceptance of such appointment. Such successor
depositary must be appointed within 60 days after delivery of the notice of
resignation or removal and must be a bank or trust company having its principal
office in the United States and having a combined capital and surplus of at
least $50 million.
 
    The depositary will forward to the holders of depositary shares all reports
and communications from us that are delivered to the depositary and that we must
furnish to the holders of the preferred stock. Neither we nor the depositary
will be liable if the depositary is prevented or delayed by law or any
circumstances beyond its control in performing its obligations under the Deposit
Agreement. Our obligations and the depositary's obligations under the Deposit
Agreement will be limited to performance in good faith of duties set forth in
the Deposit Agreement. Neither we nor the depositary will be obligated to
prosecute or defend any legal proceeding connected with any depositary shares or
preferred stock unless satisfactory indemnity is furnished. We and the
depositary may rely upon written advice of counsel or accountants, or
information provided by persons presenting preferred stock for deposit, holders
of depositary shares, or other persons believed to be competent and on documents
believed to be genuine.
 
                                       16
<PAGE>
DESCRIPTION OF THE TRUST PREFERRED SECURITIES
 
    The following descriptions of the trust preferred securities do not purport
to be complete and are subject to and qualified in their entirety by reference
to the Declaration for each Trust and the indenture between UNBC and The First
National Bank of Chicago, as trustee (the "Indenture"), relating to the issuance
of the debt securities by UNBC, as supplemented by Board resolution or by
supplemental indenture. Such documents will be filed with the SEC as an exhibit
to the registration statement of which this prospectus is a part.
 
GENERAL
 
    Each Declaration authorizes the Regular Trustees to issue on behalf of a
Trust one series of preferred securities which will have the terms described in
a prospectus supplement. The proceeds from the sale of a Trust's preferred and
common securities will be used by the Trust to purchase a series of debt
securities issued by UNBC. The debt securities will be held in trust by the
Property Trustee for the benefit of the holders of such preferred and common
securities.
 
    Under the Trust Preferred Securities Guarantee, UNBC will agree to make
payments of distributions and payments on redemption or liquidation with respect
to the Trust's preferred securities, but only to the extent such Trust has funds
available to make those payments and has not made such payments. See
"Description of the Trust Preferred Securities Guarantees."
 
    The assets of a Trust available for distribution to the holders of its
preferred securities will be limited to payments from UNBC under the series of
debt securities held by such Trust. If we fail to make a payment on such debt
securities, the Trust will not have sufficient funds to make related payments,
including distributions, on its preferred securities.
 
    Each Trust Preferred Securities Guarantee, when taken together with our
obligations under the related series of debt securities and the Indenture and
the related Declaration, will provide a full and unconditional guarantee of
amounts due on the preferred securities issued by a Trust.
 
    Each Declaration will be qualified as an indenture under the Trust Indenture
Act of 1939, as amended (the "Trust Indenture Act"). Each Property Trustee will
act as indenture trustee for the preferred securities to be issued by the
applicable Trust, in order to comply with the provisions of the Trust Indenture
Act.
 
    Each series of trust preferred securities will have the terms, including
distributions, redemption, voting, liquidation rights and such other preferred,
deferred or other special rights or such restrictions as described in the
relevant Declaration or made part of such Declaration by the Trust Indenture Act
or the Delaware Business Trust Act. The terms of such preferred securities will
mirror the terms of the debt securities held by the Trust.
 
    The prospectus supplement relating to the preferred securities of a Trust
will describe the specific terms of such preferred securities, including:
 
    - the name of such preferred securities;
 
    - the dollar amount and number of preferred securities issued;
 
    - the annual distribution rate(s) (or method of determining such rate(s)),
      the payment date(s) and the record dates used to determine the holders who
      are to receive distributions and the place(s) where distributions and
      other amounts payable will be paid;
 
    - any provision relating to deferral of distribution payments;
 
    - the date from which distributions shall be cumulative;
 
    - the optional redemption provisions, if any, including the prices, time
      periods and other terms and conditions for which such preferred securities
      shall be purchased or redeemed, in whole or in part;
 
                                       17
<PAGE>
    - the terms and conditions, if any, upon which the applicable series of debt
      securities may be distributed to holders of such preferred securities;
 
    - the voting rights, if any, of holders of such preferred securities;
 
    - any securities exchange on which such preferred securities will be listed;
 
    - whether such preferred securities are to be issued in book-entry form and
      represented by one or more global certificates, and if so, the depositary
      for such global certificates and the specific terms of the depositary
      arrangements; and
 
    - any other relevant rights, preferences, privileges, limitations or
      restrictions of such preferred securities.
 
    Each prospectus supplement will describe certain United States federal
income tax considerations applicable to the purchase, holding and disposition of
the series of trust preferred securities covered by such prospectus supplement.
 
LIQUIDATION DISTRIBUTION UPON DISSOLUTION
 
    Unless otherwise specified in the applicable prospectus supplement, each
Declaration states that the related Trust shall be dissolved:
 
    - on the expiration of the term of such Trust;
 
    - upon the bankruptcy of UNBC;
 
    - upon the filing of a certificate of dissolution or its equivalent with
      respect to UNBC;
 
    - upon the filing of a certificate of cancellation with respect to such
      Trust after obtaining the consent of at least a majority in liquidation
      amount of the preferred and common securities of such Trust, voting
      together as a single class;
 
    - 90 days after the revocation of the charter of UNBC (but only if the
      charter is not reinstated during that 90-day period);
 
    - upon the distribution of the related debt securities directly to the
      holders of the preferred and common securities of such Trust;
 
    - upon the redemption of all of the common and preferred securities of such
      Trust; or
 
    - upon entry of a court order for the dissolution of UNBC or such Trust.
 
    Unless otherwise specified in the applicable prospectus supplement, in the
event of a dissolution, after the Trust pays all amounts owed to creditors, the
holders of the preferred and common securities issued by such Trust will be
entitled to receive:
 
    - cash equal to the aggregate liquidation amount of each preferred and
      common security specified in an accompanying prospectus supplement, plus
      accumulated and unpaid distributions to the date of payment; unless
 
    - debt securities in an aggregate principal amount equal to the aggregate
      liquidation amount of the preferred and common securities are distributed
      to the holders of the preferred and common securities.
 
    If such Trust cannot pay the full amount due on its preferred and common
securities because insufficient assets are available for payment, then the
amounts payable by the Trust on its preferred and common securities shall be
paid pro rata. However, if an event of default under the related Declaration has
occurred, the total amounts due on such preferred securities will be paid before
any distribution on such common securities.
 
                                       18
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DECLARATION EVENTS OF DEFAULT
 
    An event of default under the Indenture relating to a series of debt
securities is an event of default under the Declaration of the Trust that owns
those debt securities (a "Declaration Event of Default"). See "Description of
Debt Securities--Events of Default."
 
    UNBC and the Regular Trustees of a Trust must file annually with the
Property Trustee for such Trust a certificate stating whether or not they are in
compliance with all the applicable conditions and covenants under the related
Declaration.
 
    Upon the occurrence of a Declaration Event of Default, the Property Trustee
of the applicable Trust, as the sole holder of the debt securities held by such
Trust, will have the right under the Indenture to declare the principal of,
premium, if any, and interest on such debt securities to be immediately due and
payable.
 
    If a Property Trustee fails to enforce its rights under the related
Declaration or the Indenture to the fullest extent permitted by law and subject
to the terms of the Declaration and the Indenture, any holder of the preferred
securities issued by the Trust may sue UNBC, or seek other remedies, to enforce
the Property Trustee's rights under the Declaration or the Indenture without
first instituting a legal proceeding against such Property Trustee or any other
person.
 
    If we fail to pay principal, premium, if any, or interest on a series of
debt securities when payable, then a holder of the related trust preferred
securities may directly sue us or seek other remedies, to collect its pro rata
share of payments owned.
 
REMOVAL AND REPLACEMENT OF TRUSTEES
 
    Only the holder of a Trust's common securities has the right to remove or
replace the trustees of such Trust. The resignation or removal of any trustee
and the appointment of a successor trustee shall be effective only on the
acceptance of appointment by the successor trustee in accordance with the
provisions of the Declaration for such Trust.
 
CONVERSION OR EXCHANGE RIGHTS
 
    The terms on which trust preferred securities of any series are convertible
into or exchangeable for our common stock or other securities of UNBC will be
set forth in the prospectus supplement relating thereto. Such terms will include
provisions as to whether conversion or exchange is mandatory, at the option of
the holder or at the option of UNBC, and may include provisions pursuant to
which the number of shares of our common stock or other securities of UNBC to be
received by the holders of trust preferred securities would be subject to
adjustment.
 
MERGERS, CONSOLIDATIONS OR AMALGAMATIONS OF THE TRUSTS
 
    A Trust may not consolidate, amalgamate, merge with or into, or be replaced
by, or convey, transfer or lease its properties and assets substantially as an
entirety to, any other corporation or other body ("Merger Event"), except as
described below. A Trust may, with the consent of a majority of its Regular
Trustees and without the consent of the holders of its preferred and common
securities, consolidate, amalgamate, merge with or into, or be replaced by
another Trust, provided that:
 
    - the successor entity either
 
       (1) assumes all of the obligations of the Trust relating to its preferred
           and common securities or
 
       (2) substitutes for such Trust's preferred and common securities other
           securities substantially similar to such preferred and common
           securities ("successor securities"), so long as the successor
           securities rank the same as such preferred and common securities for
           distributions and payments upon liquidation, redemption and
           otherwise;
 
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<PAGE>
    - UNBC acknowledges a trustee of such successor entity who has the same
      powers and duties as the Property Trustee of such Trust as the holder of
      the particular series of debt securities;
 
    - the preferred securities are listed, or any successor securities will be
      listed upon notice of issuance, on the same national securities exchange
      or other organization that the trust preferred securities are then listed,
      if any;
 
    - the Merger Event does not adversely affect the rights, preferences and
      privileges of the holders of its trust preferred and trust common
      securities or successor securities in any material way (other than with
      respect to any dilution of the holders' interest in the new entity);
 
    - the Merger Event does not cause the preferred securities or successor
      securities to be downgraded by any nationally recognized statistical
      rating organization;
 
    - the successor entity has a purpose identical to that of the Trust;
 
    - prior to the Merger Event, UNBC has received an opinion of counsel from a
      nationally recognized law firm stating that (a) such Merger Event does not
      adversely effect the rights, preferences and privileges of the holders of
      the preferred securities (including any successor securities) in any
      material respect and (b) following the Merger Event, neither the Trust nor
      the successor entity will be required to register as an "investment
      company" under the Investment Company Act of 1940, as amended (the
      "Investment Company Act"); and
 
    - UNBC guarantees the obligations of the successor entity under the
      successor securities in the same manner as in the applicable Trust
      Preferred Securities Guarantee and the guarantee of the common securities
      for such Trust, if any.
 
    In addition, unless all of the holders of the trust preferred and trust
common securities approve otherwise, a Trust shall not consolidate, amalgamate,
merge with or into, or be replaced by any other entity or permit any other
entity to consolidate, amalgamate, merge with or into, or replace it, if such
transaction would cause the Trust or the successor entity to be classified as
other than a grantor trust for United States federal income tax purposes.
 
VOTING RIGHTS; AMENDMENT OF DECLARATIONS
 
    The holders of trust preferred securities have no voting rights except as
discussed under "--Mergers, Consolidations or Amalgamations of the Trust,"
"--Removal and Replacement of Trustees" and "Description of the Trust Preferred
Securities Guarantees--Amendments and Assignment," and as otherwise required by
law and the Declaration for such Trust.
 
    A Declaration may be amended if approved by a majority of the Regular
Trustees of the applicable Trust. However, if any proposed amendment provides
for, or such Regular Trustees otherwise propose to effect,
 
       (1) any action that would adversely affect the powers, preferences or
           special rights of the trust's preferred and common securities,
           whether by way of amendment to such Declaration or otherwise; or
 
       (2) the dissolution, winding-up or termination of the Trust other than
           pursuant to the terms of its Declaration,
 
then the holders of the Trust's preferred and common securities as a single
class will be entitled to vote on such amendment or proposal. In that case, the
amendment or proposal will only be effective if approved by at least a majority
in liquidation amount of the trust preferred and trust common securities
affected by such amendment or proposal.
 
                                       20
<PAGE>
    If any amendment or proposal referred to in clause (1) above would adversely
affect only the preferred securities or the common securities of a Trust, then
only the affected class will be entitled to vote on such amendment or proposal
and such amendment or proposal will only be effective with the approval of at
least a majority in liquidation amount of such affected class. Notwithstanding
the foregoing, certain specified provisions of the Declaration may not be
amended without the consent of all holders of the trust's preferred and common
securities.
 
    No amendment may be made to a Declaration if such amendment would:
 
    - cause the related Trust to be characterized as other than a grantor trust
      for United States federal income tax purposes;
 
    - reduce or otherwise adversely affect the powers of the related Property
      Trustee; or
 
    - cause the related Trust to be deemed to be an "investment company" which
      is required to be registered under the Investment Company Act.
 
    The holders of a majority in aggregate liquidation amount of the preferred
securities of each Trust have the right to:
 
    - direct the time, method and place of conducting any proceeding for any
      remedy available to the Property Trustee of the Trust; or
 
    - direct the exercise of any Trust or power conferred upon such Property
      Trustee under that Trust's Declaration, including the right to direct the
      Property Trustee, as the holder of a series of debt securities, to
 
       (1) exercise the remedies available under the Indenture with respect to
           such debt securities,
 
       (2) waive any event of default under the Indenture that is waivable,
 
       (3) cancel an acceleration of the principal of the debt securities, or
 
       (4) consent to any amendment, modification or termination of the
           Indenture where consent is required.
 
    However, if the Indenture requires the consent of the holders of more than a
majority in aggregate principal amount of a series of debt securities (a
"super-majority"), then the Property Trustee for such series must get approval
of the holders of a super-majority in liquidation amount of such series of the
trust preferred securities.
 
    In addition, before taking any of the foregoing actions, the Property
Trustee must obtain an opinion of counsel from a nationally recognized law firm
stating that such action would not cause the Trust to be classified as other
than a grantor trust for United States federal income tax purposes.
 
    The Property Trustee of a Trust will notify all preferred securities holders
of such Trust of any notice received from the Trustee with respect to the debt
securities held by such Trust.
 
    As described in each Declaration, the Property Trustee may hold a meeting to
have trust preferred securities holders vote on a change or have them approve
the change by written consent.
 
    If a vote of trust preferred securities holders is taken or a consent is
obtained, any trust preferred securities that are owned by UNBC or any of our
affiliates will, for purposes of the vote or consent, be treated as if they were
not outstanding. This means that:
 
       (1) UNBC and any of our affiliates will not be able to vote on or consent
           to matters requiring the vote or consent of holders of trust
           preferred securities and
 
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<PAGE>
       (2) any trust preferred securities owned by us, the Regular Trustees or
           any of our respective affiliates will not be counted in determining
           whether the required percentage of votes or consents has been
           obtained.
 
INFORMATION CONCERNING THE PROPERTY TRUSTEES
 
    The Property Trustees will be unaffiliated with UNBC and BTM. For matters
relating to compliance with the Trust Indenture Act, the Property Trustee of
each Trust will have all of the duties and responsibilities of an indenture
trustee under the Trust Indenture Act. Each Property Trustee, other than during
the occurrence and continuance of a Declaration Event of Default under the
applicable Trust, undertakes to perform only such duties as are specifically set
forth in the applicable Declaration and, upon a Declaration Event of Default,
must use the same degree of care and skill as a prudent person would exercise or
use in the conduct of his or her own affairs. Subject to this provision, a
Property Trustee is under no obligation to exercise any of the powers given it
by the applicable Declaration at the request of any holder of trust preferred
securities unless it is offered reasonable security or indemnity against the
costs, expenses and liabilities that it might incur. However, the holders of the
trust preferred securities will not be required to offer such an indemnity where
the holders, by exercising their voting rights, direct the Property Trustee to
take any action following a Declaration Event of Default.
 
MISCELLANEOUS
 
    The Trustees of each Trust are authorized and directed to conduct the
affairs of and to operate such Trust in such a way that
 
    - the Trust will not be deemed to be an "investment company" required to be
      registered under the Investment Company Act;
 
    - the Trust will be classified as a grantor trust for United States federal
      income tax purposes; and
 
    - the debt securities held by the Trust will be treated as indebtedness of
      UNBC for United States federal income tax purposes.
 
    UNBC and the Trustees of a Trust are authorized to take any action (so long
as it is consistent with applicable law or the applicable certificate of trust
or Declaration) that we and the Trustees of such Trust determine to be necessary
or desirable for such purposes.
 
    Holders of trust preferred securities have no preemptive or similar rights.
 
    A Trust may not borrow money, issue debt, execute mortgages or pledge any of
its assets.
 
    The Property Trustee will promptly make distributions to the holders of such
Trust's preferred securities and common securities out of funds received by such
Trust from holding our debt securities.
 
GOVERNING LAW
 
    Each Declaration and the related trust preferred securities will be governed
by and construed in accordance with the laws of the State of Delaware.
 
                                       22
<PAGE>
DESCRIPTION OF DEBT SECURITIES
 
    The following descriptions of debt securities do not purport to be complete
and are subject to and qualified in their entirety by reference to the
Indenture. Such document will be filed with the SEC as an exhibit to the
registration statement of which this prospectus is a part. All capitalized terms
have the meanings specified in the Indenture.
 
    We may issue, from time to time, debt securities, in one or more series, and
will consist of either our senior debt ("Senior Debt Securities"), our senior
subordinated debt ("Senior Subordinated Debt Securities"), our subordinated debt
("Subordinated Debt Securities") or our junior subordinated debt ("Junior
Subordinated Debt Securities"). The debt securities we offer will be issued
under an Indenture between us and The First National Bank of Chicago, acting as
trustee (a "Trustee"). Debt securities, whether senior, senior subordinated,
subordinated or junior subordinated, may be issued as convertible debt
securities or exchangeable debt securities.
 
GENERAL TERMS OF THE INDENTURE
 
    The Indenture does not limit the amount of debt securities that may be
issued. It provides that debt securities may be issued up to the principal
amount that may be authorized by us and may be in any currency or currency unit
designated by us. Except for the limitations on consolidation, merger and sale
of all or substantially all of our assets contained in the Indenture, the terms
of the Indenture do not contain any covenants or other provisions designed to
afford holders of any debt securities protection with respect to our operations,
financial condition or transactions involving us.
 
    The applicable prospectus supplement for a series of debt securities to be
issued will describe, among other things, the following terms of such offered
debt securities:
 
    - the title;
 
    - any limit on the aggregate principal amount;
 
    - whether issued in fully registered form without coupons or in a form
      registered as to principal only with coupons or in bearer form with
      coupons;
 
    - whether issued in the form of one or more global securities and whether
      all or a portion of the principal amount of such debt securities is
      represented thereby;
 
    - the price or prices at which such debt securities will be issued;
 
    - the date or dates on which principal is payable;
 
    - the place or places where and the manner in which principal, premium or
      interest will be payable and the place or places where such debt
      securities may be presented for transfer and, if applicable, conversion or
      exchange;
 
    - interest rates, and the dates from which such interest, if any, will
      accrue, and the dates when such interest is payable and the maturity;
 
    - the right, if any, to extend the interest payment periods and the duration
      of the extensions;
 
    - our rights or obligations to redeem or purchase such debt securities;
 
    - conversion or exchange provisions, if any, including conversion or
      exchange prices or rates and adjustments thereto;
 
    - the currency or currencies of payment of principal or interest;
 
    - the terms applicable to any debt securities issued at a discount from
      their stated principal amount;
 
    - the terms, if any, pursuant to which any debt securities will be
      subordinate to any of our debt;
 
                                       23
<PAGE>
    - if the amount of payments of principal or interest is to be determined by
      reference to an index or formula, or based on a coin or currency other
      than that in which such debt securities are stated to be payable, the
      manner in which such amounts are determined and the calculation agent, if
      any, with respect thereto;
 
    - if other than the principal amount of the debt securities when issued, the
      portion of the principal amount payable upon acceleration of maturity as a
      result of a default on certain of our obligations;
 
    - if applicable, covenants affording holders of debt protection with respect
      to our operations, financial condition or transactions involving us; and
 
    - any other specific terms of any debt securities.
 
    The applicable prospectus supplement will set forth certain United States
federal income tax considerations for holders of any debt securities and the
securities exchange or quotation system on which any debt securities are listed
or quoted.
 
SENIOR DEBT SECURITIES
 
    Payment of the principal of, premium, if any, and interest on Senior Debt
Securities will rank on a parity with all of our other unsecured and
unsubordinated debt.
 
SENIOR SUBORDINATED DEBT SECURITIES
 
    Payment of the principal of, premium, if any, and interest on Senior
Subordinated Debt Securities will be junior in right of payment to the prior
payment in full of all of our unsubordinated debt. We will set forth in the
applicable prospectus supplement relating to any Senior Subordinated Debt
Securities the subordination terms of such securities as well as the aggregate
amount of outstanding debt, as of the most recent practicable date, that by its
terms would be senior to the Senior Subordinated Debt Securities. We will also
set forth in such prospectus supplement limitations, if any, on issuance of
additional senior debt.
 
SUBORDINATED DEBT SECURITIES
 
    Payment of the principal of, premium, if any, and interest on Subordinated
Debt Securities will be subordinated and junior in right of payment to the prior
payment in full of all of our senior debt. We will set forth in the applicable
prospectus supplement relating to any Subordinated Debt Securities the
subordination terms of such securities as well as the aggregate amount of
outstanding indebtedness, as of the most recent practicable date, that by its
terms would be senior to the Subordinated Debt Securities. We will also set
forth in such prospectus supplement limitations, if any, on issuance of
additional senior indebtedness.
 
JUNIOR SUBORDINATED DEBT SECURITIES
 
    Payment of the principal of, premium, if any, and interest on Junior
Subordinated Debt Securities will be subordinated and junior in right of payment
to the prior payment in full of all of our senior, senior subordinated and
subordinated debt. We will set forth in the applicable prospectus supplement
relating to any Junior Subordinated Debt Securities the subordination terms of
such securities as well as the aggregate amount of outstanding debt, as of the
most recent practicable date, that by its terms would be senior to the Junior
Subordinated Debt Securities. We will also set forth in such prospectus
supplement limitations, if any, on issuance of additional senior indebtedness.
 
                                       24
<PAGE>
CONVERSION OR EXCHANGE RIGHTS
 
    Debt securities may be convertible into or exchangeable for shares of UNBC's
equity securities. The terms and conditions of such conversion or exchange will
be set forth in the applicable prospectus supplement. Such terms will include,
among others, the following:
 
    - the conversion or exchange price;
 
    - the conversion or exchange period;
 
    - provisions regarding the ability of us or the holder to convert or
      exchange the debt securities;
 
    - events requiring adjustment to the conversion or exchange price; and
 
    - provisions affecting conversion or exchange in the event of our redemption
      of such debt securities.
 
CONSOLIDATION, MERGER OR SALE
 
    We cannot consolidate or merge with or into, or transfer or lease all or
substantially all of our assets to, any person unless (i) we will be the
continuing corporation or (ii) the successor corporation or person to which our
assets are transferred or leased is a corporation organized under the laws of
the U.S., any state of the U.S. or the District of Columbia and expressly
assumes our obligations on the debt securities and under the Indenture. In
addition, we cannot effect such a transaction unless immediately after giving
effect to such transaction, no Event of Default shall have occurred and be
continuing. Subject to certain exceptions, when the person to which our assets
are transferred or leased has assumed our obligations under the debt securities
and the Indenture, we shall be discharged from all our obligations under the
debt securities and the Indenture.
 
    This covenant would not apply to any recapitalization transaction, a change
of control of UNBC or a highly leveraged transaction, unless such transaction or
change of control were structured to include a merger or consolidation or
transfer or lease of all or substantially all of our assets.
 
EVENTS OF DEFAULT
 
    Unless otherwise indicated, the term "Event of Default," when used in the
Indenture, means any of the following:
 
    - failure to pay interest for 30 days after the date payment is due and
      payable; provided that a valid extension of an interest payment period by
      UNBC in accordance with the terms of the debt securities shall not
      constitute a failure to pay interest;
 
    - failure to pay principal or premium, if any, on any debt security when
      due, either at maturity, upon any redemption, by declaration or otherwise;
 
    - failure to make sinking fund payments when due;
 
    - failure to perform any other covenant for 90 days after notice that
      performance was required;
 
    - certain events in bankruptcy, insolvency or reorganization of UNBC; or
 
    - any other Event of Default provided in the applicable resolution of our
      Board or the supplemental indenture under which such series of debt
      securities is issued.
 
                                       25
<PAGE>
    An Event of Default for a particular series of debt securities does not
necessarily constitute an Event of Default for any other series of debt
securities issued under the Indenture. IF AN EVENT OF DEFAULT RELATING TO THE
PAYMENT OF INTEREST, PRINCIPAL OR ANY SINKING FUND INSTALLMENT WITH RESPECT TO
ANY SERIES OF DEBT SECURITIES SHALL HAVE OCCURRED AND BE CONTINUING, THE TRUSTEE
OR THE HOLDERS OF NOT LESS THAN 25% IN AGGREGATE PRINCIPAL AMOUNT OF THE DEBT
SECURITIES OF SUCH SERIES MAY DECLARE THE ENTIRE PRINCIPAL OF ALL THE DEBT
SECURITIES OF SUCH SERIES TO BE DUE AND PAYABLE IMMEDIATELY. IF AN EVENT OF
DEFAULT INVOLVING CERTAIN EVENTS IN BANKRUPTCY, INSOLVENCY OR REORGANIZATION OF
UNBC OR ANOTHER EVENT OF DEFAULT UNDER A PARTICULAR SERIES OF DEBT SECURITIES
SHALL HAVE OCCURRED AND BE CONTINUING, THE TRUSTEE OR THE HOLDERS OF NOT LESS
THAN 25% IN THE AGGREGATE PRINCIPAL AMOUNT OF EACH AFFECTED SERIES OF DEBT
SECURITIES MAY DECLARE THE ENTIRE PRINCIPAL AMOUNT OF THEIR RESPECTIVE DEBT
SECURITIES TO BE DUE AND PAYABLE IMMEDIATELY. Subject to certain conditions, the
holders of not less than a majority in aggregate principal amount of the debt
securities of a series may rescind and annul any such declarations and
consequences with respect to such series.
 
    The Indenture imposes limitations on suits brought by holders of debt
securities against us. No holder of debt securities of any series may institute
any action against us under the Indenture (except actions for payment of overdue
principal, premium, if any, or interest) unless (i) such holder has previously
given to the Trustee written notice of default and continuance of such default,
(ii) the holders of at least 25% in principal amount of the outstanding debt
securities of the affected series have requested that the Trustee institute such
action, (iii) such requesting holders have offered the Trustee reasonable
indemnity for expenses and liabilities that may be incurred by bringing such
action, (iv) the Trustee has not instituted such action within 60 days of such
request and (v) the Trustee has not received inconsistent direction by the
holders of a majority in principal amount of the outstanding debt securities of
such series.
 
    We will be required to file annually with the Trustee a certificate, signed
by an officer of UNBC, stating whether or not such officer knows of any default
by us in the performance, observance or fulfillment of any condition or covenant
of the Indenture.
 
REGISTERED GLOBAL SECURITIES
 
    We may issue the debt securities of a series in whole or in part in the form
of one or more fully registered global securities (a "Registered Global
Security") that will be deposited with a depositary or with a nominee for a
depositary identified in the applicable prospectus supplement and registered in
the name of such depositary or nominee. In such case, we will issue one or more
Registered Global Securities denominated in an amount equal to the aggregate
principal amount of all of the debt securities of the series to be issued and
represented by such Registered Global Security or Securities. Unless and until
it is exchanged in whole or in part for debt securities in definitive registered
form, a Registered Global Security may not be transferred except as a whole (i)
by the depositary for such Registered Global Security to its nominee or, (ii) by
a nominee of the depositary to the depositary or another nominee of the
depositary or (iii) by the depositary or its nominee to a successor of the
depositary or a nominee of the successor.
 
    The prospectus supplement relating to a series of debt securities will
describe the specific terms of the depositary arrangement with respect to any
portion of such series represented by a Registered Global Security. We
anticipate that the following provisions will apply to all depositary
arrangements for debt securities:
 
    - ownership of beneficial interests in a Registered Global Security will be
      limited to persons that have accounts with the depositary for such
      Registered Global Security, such persons being referred to as
      "participants," or persons that may hold interests through participants;
 
    - upon the issuance of a Registered Global Security, the depositary for such
      Registered Global Security will credit, on its book-entry registration and
      transfer system, the participants' accounts with the respective principal
      amounts of the debt securities represented by such Registered Global
      Security beneficially owned by such participants;
 
                                       26
<PAGE>
    - any dealers, underwriters, or agents participating in the distribution of
      such debt securities will designate the accounts to be credited; and
 
    - ownership of beneficial interest in such Registered Global Security will
      be shown on, and the transfer of such ownership interest will be effected
      only through, records maintained by the depositary for such Registered
      Global Security (with respect to interests of participants) and on the
      records of participants (with respect to interests of persons holding
      through participants).
 
    The laws of some states may require that certain purchasers of securities
take physical delivery of the securities in definitive form. These laws may
limit the ability of certain persons to own, transfer or pledge beneficial
interests in Registered Global Securities.
 
    So long as the depositary for a Registered Global Security, or its nominee,
is the registered owner of such Registered Global Security, the depositary or
such nominee, as the case may be, will be considered the sole owner or holder of
the debt securities represented by such Registered Global Security for all
purposes under the Indenture. Except as set forth below, owners of beneficial
interests in a Registered Global Security will not be entitled to have the debt
securities represented by such Registered Global Security registered in their
names, will not receive or be entitled to receive physical delivery of such debt
securities in the definitive form and will not be considered the owners or
holders of such debt securities under the Indenture. Accordingly, each person
owning a beneficial interest in a Registered Global Security must rely on the
procedures of the depositary for such Registered Global Security and, if such
person is not a participant, on the procedures of a participant through which
such person owns its interest, to exercise any rights of a holder under the
Indenture. We understand that under existing industry practices, if we request
any action of holders or if an owner of a beneficial interest in a Registered
Global Security desires to give or take any action which a holder is entitled to
give or take under the Indenture, the depositary for such Registered Global
Security would authorize the participants holding the relevant beneficial
interests to give or take such action, and such participants would authorize
beneficial owners owning through such participants to give or take such action
or would otherwise act upon the instructions of beneficial owners holding
through them.
 
    Payments of principal and premium, if any, and interest, if any, of debt
securities represented by a Registered Global Security registered in the name of
a depositary or its nominee will be made to such depositary or its nominee, as
the case may be, as the registered owners of the Registered Global Security.
None of us, the Trustee or any other agent of us or the Trustee will be
responsible or liable for any aspect of the records relating to or payments made
on account of beneficial ownership interests in such Registered Global Security
or for maintaining, supervising or reviewing any records relating to such
beneficial ownership interests.
 
    We expect that the depositary for any debt securities represented by a
Registered Global Security, upon receipt of any payments of principal and
premium, if any, and interest, if any, in respect of such Registered Global
Security, will immediately credit participants' accounts with payments in
amounts proportionate to their respective beneficial interests in such
Registered Global Security as shown on the records of the depositary. We also
expect that standing customer instructions and customary practices will govern
payments by participants to owners of beneficial interests in such Registered
Global Security held through such participants, as is now the case with the
securities held for the accounts of customers in bearer form or registered in
"street name." We also expect that any such payments will be the responsibility
of such participants.
 
    If the depositary for any debt securities represented by a Registered Global
Security is at any time unwilling or unable to continue as depositary or ceases
to be a clearing agency registered under the Securities Exchange Act, we will
appoint an eligible successor depositary. If we fail to appoint an eligible
successor depositary within 90 days, we will issue such debt securities in
definitive form in exchange for such Registered Global Security. In addition, we
may at any time and in our sole discretion decide not to have any of the debt
securities of a series represented by one or more Registered Global Securities
and, in
 
                                       27
<PAGE>
such event, will issue debt securities of such series in a definitive form in
exchange for all of the Registered Global Security or Securities representing
such debt securities. The Trustee will register any debt securities issued in
definitive form in exchange for a Registered Global Security in such name or
names as the depositary, based upon instructions from its participants, shall
instruct the Trustee.
 
    Bearer debt securities of a series may also be issued in the form of one or
more global securities, referred to as "bearer global securities," that will be
deposited with a common depositary for Euroclear System and Cedel Bank, SOCIETE
ANONYME, or with a nominee for such depositary identified in the prospectus
supplement relating to such series. The prospectus supplement relating to a
series of debt securities represented by a bearer global security will describe
the specific terms and procedures including the specific terms of the depositary
arrangement and any specific procedures for the issuance of debt securities in
definitive form in exchange for a bearer global security, with respect to the
position of such series represented by a bearer global security.
 
DISCHARGE, DEFEASANCE AND COVENANT DEFEASANCE
 
    We can discharge or decrease our obligations under the Indenture as set
forth below.
 
    We may discharge certain obligations to holders of any series of debt
securities that have not already been delivered to the Trustee for cancellation
and that have either become due and payable or are by their terms to become due
and payable within one year (or are scheduled for redemption within one year).
Such discharge may be affected by our irrevocably depositing with the Trustee
cash or U.S. Government Obligations, as trust funds, in an amount certified to
be sufficient to pay when due, whether at maturity, upon redemption or
otherwise, the principal of, premium, if any, and interest on such debt
securities and any mandatory sinking fund payments.
 
    Unless otherwise provided in the applicable prospectus supplement, we may
also discharge any and all of our obligations to holders of any series of debt
securities at any time ("defeasance"). We may be released with respect to any
outstanding series of debt securities from the obligations imposed by any
covenants imposed by such series of debt securities and certain provisions of
the Indenture, and we may omit to comply with such covenants without creating an
Event of Default ("covenant defeasance"). Defeasance and covenant defeasance may
be effected only if, among other things: (i) we irrevocably deposit with the
Trustee cash or U.S. Government Obligations, as trust funds, in an amount
certified to be sufficient to pay at maturity (or upon redemption) the
principal, premium, if any, and interest on all outstanding debt securities of
such series; (ii) we deliver to the Trustee an opinion of counsel from a
nationally recognized law firm to the effect that the holders of such series of
debt securities will not recognize income, gain or loss for U.S. federal income
tax purposes as a result of such defeasance or covenant defeasance and that
defeasance or covenant defeasance will not otherwise alter such holders' U.S.
federal income tax treatment of principal, premium, if any, and interest
payments on such series of debt securities and (iii) in the case of subordinated
debt securities, no event or condition shall exist that, pursuant to the
subordination provisions applicable to such series, would prevent us from making
payments of principal of, premium, if any, and interest on any of such
subordinated debt securities at the date of the irrevocable deposit referred to
above or at any time during the period ending on the 91st day after such deposit
date. In the case of a defeasance by us, the opinion we deliver must be based on
a ruling of the Internal Revenue Service issued, or a change in U.S. federal
income tax law occurring, after                         , 1998, since such a
result would not occur under the U.S. federal income tax laws in effect on such
date.
 
    Although we may discharge or decrease our obligations under the Indenture as
described in the two preceding paragraphs, we may not avoid, among other things,
our duty to register the transfer or exchange of any series of debt securities,
to replace any temporary, mutilated, destroyed, lost or stolen series of debt
securities or to maintain an office or agency in respect of any series of debt
securities.
 
                                       28
<PAGE>
MODIFICATION OF THE INDENTURE
 
    The Indenture provides that we and the Trustee may enter into supplemental
indentures without the consent of the holders of debt securities to: (i) secure
any debt securities, (ii) evidence the assumption by a successor corporation of
our obligations, (iii) add covenants for the protection of the holders of debt
securities, (iv) cure any ambiguity or correct any inconsistency in the
Indenture, (v) establish the forms or terms of debt securities of any series and
(vi) evidence and provide for the acceptance of appointment by a successor
trustee.
 
    The Indenture also provides that we and the Trustee may, with the consent of
the holders of not less than a majority in aggregate principal amount of debt
securities of all series then outstanding and affected (voting as one class),
add any provisions to, or change in any manner, eliminate or modify in any way
the provisions of, the Indenture or modify in any manner the rights of the
holders of such debt securities. We and the Trustee may not, however, without
the consent of the holder of each outstanding debt security affected thereby:
 
    - extend the final maturity of any debt security;
 
    - reduce the principal amount or premium, if any;
 
    - reduce the rate or extend the time of payment of interest;
 
    - reduce any amount payable on redemption;
 
    - change the currency in which the principal (other than as otherwise may be
      provided with respect to such series), premium, if any, or interest is
      payable;
 
    - reduce the amount of the principal of any debt security issued with an
      original issue discount that is payable upon acceleration or provable in
      bankruptcy;
 
    - alter certain provisions of the Indenture relating to the debt securities
      not denominated in U.S. dollars;
 
    - impair the right to institute suit for the enforcement of any payment on
      any debt security when due; or
 
    - reduce the percentage of holders of debt securities of any series whose
      consent is required for any modification of the Indenture.
 
CONCERNING THE TRUSTEE
 
    The Indenture provides that there may be more than one Trustee under the
Indenture, each with respect to one or more series of debt securities. If there
are different Trustees for different series of debt securities, each Trustee
will be a Trustee of a Trust under the Indenture separate and apart from the
Trust administered by any other Trustee under the Indenture. Except as otherwise
indicated in this prospectus or any prospectus supplement, any action permitted
to be taken by a Trustee may be taken by such Trustee only with respect to the
one or more series of debt securities for which it is the Trustee under the
Indenture. Any Trustee under the Indenture may resign or be removed with respect
to one or more series of debt securities. All payments of principal of, premium,
if any, and interest on, and all registration, transfer, exchange,
authentication and delivery (including authentication and delivery on original
issuance of the debt securities) of, the debt securities of a series will be
effected by the Trustee with respect to such series at an office designated by
such Trustee in New York, New York.
 
    The Indenture contains certain limitations on the right of the Trustee,
should it become a creditor of UNBC, to obtain payment of claims in certain
cases or to realize on certain property received in respect of any such claim as
security or otherwise. The Trustee may engage in other transactions; however, if
it acquires any conflicting interest relating to any duties with respect to the
debt securities it must eliminate such conflict or resign as Trustee.
 
                                       29
<PAGE>
    The holders of a majority in principal amount of any series of debt
securities then outstanding will have the right to direct the time, method and
place of conducting any proceeding for exercising any remedy available to the
Trustee with respect to such series of debt securities, provided that such
direction would not conflict with any rule of law or with the Indenture, would
not be unduly prejudicial to the rights of another holder of the debt
securities, and would not involve any Trustee in personal liability. The
Indenture provides that in case an Event of Default shall occur and be known to
any Trustee (and not be cured), such Trustee must use the degree of care of a
prudent person in the conduct of his or her own affairs in the exercise of its
power. Subject to such provisions, the Trustee will be under no obligation to
exercise any of its rights or powers under the Indenture at the request of any
of the holders of the debt securities, unless they shall have offered to the
Trustee security and indemnity satisfactory to the Trustee.
 
NO INDIVIDUAL LIABILITY OF INCORPORATORS, SHAREHOLDERS, OFFICERS OR DIRECTORS
 
    The Indenture provides that no incorporator and no past, present or future
shareholder, officer or director, of UNBC or any successor corporation in their
capacity as such shall have any individual liability for any of our obligations,
covenants or agreements under the debt securities or the Indenture.
 
GOVERNING LAW
 
    The Indenture and the debt securities will be governed by, and construed in
accordance with, the laws of the state of New York.
 
DESCRIPTION OF THE TRUST PREFERRED SECURITIES GUARANTEES
 
    The following descriptions of the trust preferred securities guarantees do
not purport to be complete and are subject to and qualified in their entirety by
reference to our guarantee of the preferred securities issued by each Trust (the
"Trust Preferred Securities Guarantees"). Such document will be filed with the
SEC as an exhibit to the registration statement of which this prospectus is a
part.
 
GENERAL
 
    UNBC will execute a Trust Preferred Securities Guarantee, which benefits the
holders of trust preferred securities, at the time that a Trust issues those
trust preferred securities. Each Trust Preferred Securities Guarantee will be
qualified as an indenture under the Trust Indenture Act. Unless otherwise stated
in a prospectus supplement, The First National Bank of Chicago will act as
indenture trustee ("Trust Preferred Guarantee Trustee") under each Trust
Preferred Securities Guarantee for the purposes of compliance with the Trust
Indenture Act. The Trust Preferred Guarantee Trustee will hold each Trust
Preferred Securities Guarantee for the benefit of the preferred securities
holders of the applicable Trust.
 
    UNBC will agree, as described in each Trust Preferred Securities Guarantee,
to pay in full, to the holders of the trust preferred securities issued by the
applicable Trust, the Trust Preferred Securities Guarantee Payments (as defined)
(except to the extent previously paid), when and as due, regardless of any
defense, right of set-off or counterclaim which such Trust may have or assert.
The following payments, to the extent not paid by a Trust ("Trust Preferred
Securities Guarantee Payments"), will be covered by the applicable Trust
Preferred Securities Guarantee:
 
    - any accrued and unpaid distributions required to be paid on the applicable
      trust preferred securities, to the extent that the Trust has funds
      available to make the payment;
 
    - the redemption price, to the extent that the Trust has funds available to
      make the payment; and
 
    - upon a voluntary or involuntary dissolution and liquidation of the Trust
      (other than in connection with a distribution of debt securities to
      holders of such trust preferred securities or the redemption of all such
      trust preferred securities), the lesser of
 
                                       30
<PAGE>
       (1) the aggregate of the liquidation amount specified in the prospectus
           supplement for each trust preferred security plus all accrued and
           unpaid distributions on the trust preferred securities to the date of
           payment, to the extent the Trust has funds available to make the
           payment and
 
       (2) the amount of assets of the Trust remaining available for
           distribution to holders of its trust preferred securities upon a
           dissolution and liquidation of the Trust ("Liquidation Payment").
 
    Our obligation to make a Trust Preferred Securities Guarantee Payment may be
satisfied by directly paying the required amounts to the holders of the trust
preferred securities or by causing the Trust to pay the amounts to the holders.
 
    No single document executed by UNBC relating to the issuance of trust
preferred securities will provide for its full, irrevocable and unconditional
guarantee of the trust preferred securities. It is only the combined operation
of our obligations under the Indenture and the applicable Trust Preferred
Securities Guarantee and Declaration that has the effect of providing a full,
irrevocable and unconditional guarantee of a Trust's obligations under its trust
preferred securities.
 
STATUS OF THE TRUST PREFERRED SECURITIES GUARANTEES
 
    Each Trust Preferred Securities Guarantee will constitute an unsecured
obligation of UNBC and will rank:
 
    - subordinate and junior in right of payment to all of our other liabilities
      (except those obligations made equal or junior to its obligations under a
      Trust Preferred Securities Guarantee);
 
    - equal with the most senior preferred or preference stock now or hereafter
      issued by us, and with any guarantee now or hereafter issued by it in
      respect of any preferred or preference stock of any of its affiliates; and
 
    - senior to our Common Stock.
 
    Each Declaration will require that the holder of trust preferred securities
accept the subordination provisions and other terms of the Trust Preferred
Securities Guarantee. Each Trust Preferred Securities Guarantee will constitute
a guarantee of payment and not of collection (in other words the holder of the
guaranteed security may sue us, or seek other remedies, to enforce its rights
under the Trust Preferred Securities Guarantee without first suing any other
person or entity). A Trust Preferred Securities Guarantee will not be discharged
except by payment of the Trust Preferred Securities Guarantee Payments in full
to the extent not previously paid or upon distribution to the applicable trust
preferred securities holders of the corresponding series of debt securities
pursuant to the appropriate Declaration.
 
AMENDMENTS AND ASSIGNMENT
 
    Except with respect to any changes which do not adversely affect the rights
of holders of trust preferred securities in any material respect (in which case
no consent of such holders will be required), a Trust Preferred Securities
Guarantee may only be amended with the prior approval of the holders of at least
a majority in aggregate liquidation amount of such trust preferred securities
(excluding any such trust preferred securities held by us or any of our
affiliates). A description of the way to obtain any approval is described under
"Description of the Trust Preferred Securities--Voting Rights; Amendment of
Declarations." All guarantees and agreements contained in the Trust Preferred
Securities Guarantee will be binding on our successors, assigns, receivers,
trustees and representatives and are for the benefit of the holders of the
applicable trust preferred securities.
 
                                       31
<PAGE>
TRUST PREFERRED SECURITIES GUARANTEE EVENTS OF DEFAULT
 
    An event of default under a Trust Preferred Securities Guarantee occurs if
we fail to make any of our required payments or perform its obligations under
such Trust Preferred Securities Guarantee.
 
    The holders of at least a majority in aggregate liquidation amount of the
trust preferred securities relating to each Trust Preferred Securities Guarantee
(excluding any trust preferred securities held by the Company or any of its
affiliates) will have the right to direct the time, method and place of
conducting any proceeding for any remedy available to the Trust Preferred
Guarantee Trustee relating to such Trust Preferred Securities Guarantee or to
direct the exercise of any Trust or power given to the Trust Preferred Guarantee
Trustee under such Trust Preferred Securities Guarantee.
 
INFORMATION CONCERNING THE TRUST PREFERRED GUARANTEE TRUSTEE
 
    The Trust Preferred Guarantee Trustee under a Trust Preferred Securities
Guarantee, other than during the occurrence and continuance of a default under
such Trust Preferred Securities Guarantee, will only perform the duties that are
specifically described in such Trust Preferred Securities Guarantee. After such
a default, the Trust Preferred Guarantee Trustee will exercise the same degree
of care and skill as a prudent person would exercise or use in the conduct of
his or her own affairs. Subject to this provision, a Trust Preferred Guarantee
Trustee is under no obligation to exercise any of its powers as described in the
applicable Trust Preferred Securities Guarantee at the request of any holder of
covered trust preferred securities unless it is offered reasonable indemnity
against the costs, expenses and liabilities that it might incur.
 
TERMINATION OF THE TRUST PREFERRED SECURITIES GUARANTEE
 
    Each Trust Preferred Securities Guarantee will terminate once the applicable
trust preferred securities are paid in full or upon distribution of the
corresponding series of debt securities to the holders of such trust preferred
securities. Each Trust Preferred Securities Guarantee will continue to be
effective or will be reinstated if at any time any holder of trust preferred
securities issued by the applicable Trust must restore payment of any sums paid
under such trust preferred securities or such Trust Preferred Securities
Guarantee.
 
GOVERNING LAW
 
    The Trust Preferred Securities Guarantees will be governed by and construed
in accordance with the laws of the state of New York.
 
                                       32
<PAGE>
     RELATIONSHIP AMONG THE TRUST PREFERRED SECURITIES, THE TRUST PREFERRED
        SECURITIES GUARANTEE AND THE DEBT SECURITIES HELD BY EACH TRUST
 
    Payments of distributions and redemption and liquidation payments due on
each series of the trust preferred securities (to the extent the applicable
Trust has funds available for the payments) will be guaranteed by UNBC to the
extent described under "Description of the Trust Preferred Securities
Guarantees." No single document executed by us in connection with the issuance
of any series of the trust preferred securities will provide for its full,
irrevocable and unconditional guarantee of such trust preferred securities. It
is only the combined operation of our obligations under the applicable Trust
Preferred Securities Guarantee, Declaration and the Indenture that has the
effect of providing a full, irrevocable and unconditional guarantee of the
Trust's obligations under its trust preferred securities.
 
    As long as we make payments of interest and other payments when due on the
debt securities held by a Trust, such payments will be sufficient to cover the
payment of distributions and redemption and liquidation payments due on the
trust preferred securities issued by that Trust, primarily because:
 
    - the aggregate principal amount of the debt securities will be equal to the
      sum of the aggregate liquidation amount of the trust preferred and trust
      common securities;
 
    - the interest rate and interest and other payment dates on the debt
      securities will match the distribution rate and distribution and other
      payment dates for the trust preferred securities;
 
    - we shall pay for any and all costs, expenses and liabilities of each Trust
      except such Trust's obligations under its trust preferred securities; and
 
    - each Declaration provides that the related Trust will not engage in any
      activity that is not consistent with the limited purposes of the Trust.
 
    If and to the extent that we do not make payments on such debt securities,
such Trust will not have funds available to make payments of distributions or
other amounts due on its trust preferred securities. In those circumstances, you
will not be able to rely upon the Trust Preferred Securities Guarantee for
payment of these amounts. Instead, you may directly sue us or seek other
remedies to collect your pro rata share of payments owed. If you sue us to
collect payment, then we will assume your rights as a holder of trust preferred
securities under such Trust's Declaration to the extent we make a payment to you
in any such legal action.
 
    A holder of any trust preferred security may sue us, or seek other remedies,
to enforce its rights under the Preferred Securities Guarantee without first
suing the applicable Preferred Guarantee Trustee, the Trust which issued the
preferred security or any other person or entity.
 
                              PLAN OF DISTRIBUTION
 
    UNBC may sell common stock, preferred stock, depositary shares or any series
of debt securities and a Trust may sell trust preferred securities being offered
hereby in one or more of the following ways from time to time:
 
    - to underwriters or dealers for resale to the public or to institutional
      investors;
 
    - directly to institutional investors; or
 
    - through agents to the public or to institutional investors.
 
    The prospectus supplements will set forth the terms of the offering of the
securities, including the name or names of any underwriters or agents, the
purchase price of such securities and the proceeds to UNBC or the applicable
Trust, as the case may be, from such sale, any underwriting discounts or agency
fees and other items constituting underwriters' or agents' compensation, any
initial public offering price,
 
                                       33
<PAGE>
any discounts or concessions allowed or reallowed or paid to dealers and any
securities exchanges on which such securities may be listed.
 
    If underwriters are used in the sale, the securities will be acquired by the
underwriters for their own account and may be resold from time to time in one or
more transactions, including negotiated transactions, at a fixed public offering
price or at varying prices determined at the time of sale.
 
    If a dealer is used in the sale, UNBC and/or a Trust, as the case may be,
will sell such securities to the dealer, as principal. The dealer may then
resell such securities to the public at varying prices to be determined by such
dealer at the time for resale.
 
    Unless otherwise set forth in a prospectus supplement, the obligations of
the underwriters to purchase any series of securities will be subject to certain
conditions precedent and the underwriters will be obligated to purchase all of
such series of securities, if any are purchased.
 
    Underwriters and agents may be entitled under agreements entered into with
the Company and/or a Trust to indemnification by UNBC and/or such Trust against
certain civil liabilities, including liabilities under the Securities Act, or to
contribution with respect to payments which the underwriters or agents may be
required to make in respect thereof. Underwriters and agents may be customers
of, engage in transactions with, or perform services for us and our affiliates
in the ordinary course of business.
 
    Other than the Common Stock which is listed on the NMS, each of the
securities issued hereunder will be new issues of securities and will have no
prior trading market. Any Common Stock sold pursuant to a prospectus supplement
will be quoted on the NMS, subject to official notice of issuance. Any
underwriters to whom securities are sold by UNBC or by the Trusts for public
offering and sale may make a market in the securities, but such underwriters
will not be obligated to do so and may discontinue any market making at any time
without notice. The securities may or may not be listed on a national securities
exchange.
 
                                 LEGAL OPINIONS
 
    The validity of the securities being offered hereby is being passed upon for
UNBC and each Trust by Skadden, Arps, Slate, Meagher & Flom LLP, Los Angeles,
California.
 
                                    EXPERTS
 
    The consolidated financial statements incorporated in this prospectus by
reference from UNBC's Annual Report on Form 10-K/A have been audited by Deloitte
& Touche LLP, independent auditors, as stated in their report incorporated in
this prospectus by reference, and have been so incorporated in reliance upon the
report of such firm given upon their authority as experts in accounting and
auditing. The consolidated financial statements give retroactive effect to the
1996 merger of BanCal Tri-State Corporation and Union Bank which has been
accounted for as a pooling-of-interests. The consolidated statements of income,
changes in shareholders' equity, and cash flows of Union Bank and its
subsidiaries for the year ended December 31, 1995 (not presented separately in
UNBC's 1997 Annual Report on Form 10-K/A) were audited by Arthur Andersen LLP,
independent auditors, as stated in their report incorporated by reference
herein.
 
                                       34
<PAGE>
                                    PART II
                     INFORMATION NOT REQUIRED IN PROSPECTUS
 
ITEM 14.  OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION
 
    The following table sets forth the expenses to be borne by the Company and
BTM in connection with the offerings described in this Registration Statement.
All such expenses other than the Securities and Exchange Commission registration
fee are estimates.
 
<TABLE>
<S>                                                                 <C>
Securities and Exchange Commission Registration Fee...............  $ 208,500
Transfer Agents, Trustees and Depositary's Fees and Expenses......
Printing and Engraving Fees and Expenses..........................
Accounting Fees and Expenses......................................
Blue Sky Fees and Expenses........................................
Legal Fees........................................................
Rating Agency Fees................................................
Miscellaneous (including Listing Fees, if applicable).............
                                                                    ---------
    Total.........................................................  $
                                                                    ---------
                                                                    ---------
</TABLE>
 
ITEM 15.  INDEMNIFICATION OF DIRECTORS AND OFFICERS
 
    As authorized by Section 317 of the CGCL, each director and officer of UNBC
may be indemnified by UNBC against expenses (including attorney's fees,
judgments, fines and amounts paid in settlement) actually and reasonably
incurred in connection with the defense or settlement of any threatened, pending
or completed legal proceedings in which such person is involved by reason of the
fact that such person is or was a director or officer of UNBC if such person
acted in good faith and in a manner that such person reasonably believed to be
in the best interests of UNBC and, with respect to any criminal action or
proceeding, if such person had no reasonable cause to believe that his conduct
was unlawful. If the legal proceeding, however, is by or in the right of UNBC,
the director or officer may not be indemnified in respect of any claim, issue or
matter as to which such person shall have been adjudged to be liable for
negligence or misconduct in the performance of his duty to UNBC unless a court
determines otherwise.
 
    In addition, we maintain a directors' and officers' liability policy.
 
    Article VII of the Articles of Incorporation and Section 55 of the Bylaws
provide that, to the fullest extent permitted by law, directors of UNBC will not
be liable for monetary damages to UNBC or its shareholders for breaches of their
fiduciary duties.
 
ITEM 16.  EXHIBITS
 
    The following is a list of all exhibits filed as a part of this Registration
Statement on Form S-3, including those incorporated herein by reference.
 
<TABLE>
<CAPTION>
EXHIBIT
NUMBER DESCRIPTION OF EXHIBITS
- ------ --------------------------------------------------------------------------
<C>    <S>
 
  4.1* Form of Common Stock
 
  4.2  Certificate of Trust of UnionBanCal Finance Trust I
 
  4.3  Certificate of Trust of UnionBanCal Finance Trust II
 
  4.4  Certificate of Trust of UnionBanCal Finance Trust III
 
  4.5  Certificate of Trust of UnionBanCal Finance Trust IV
 
  4.6* Declaration of Trust of UnionBanCal Finance Trust I
</TABLE>
 
                                      II-1
<PAGE>
<TABLE>
<CAPTION>
EXHIBIT
NUMBER DESCRIPTION OF EXHIBITS
- ------ --------------------------------------------------------------------------
<C>    <S>
  4.7* Declaration of Trust of UnionBanCal Finance Trust II
 
  4.8* Declaration of Trust of UnionBanCal Finance Trust III
 
  4.9* Declaration of Trust of UnionBanCal Finance Trust IV
 
  4.10* Form of Amended and Restated Declaration of Trust of UnionBanCal Finance
         Trust I
 
  4.11* Form of Amended and Restated Declaration of Trust of UnionBanCal Finance
         Trust II
 
  4.12* Form of Amended and Restated Declaration of Trust of UnionBanCal Finance
         Trust III
 
  4.13* Form of Amended and Restated Declaration of Trust of UnionBanCal Finance
         Trust IV
 
  4.14* Form of Indenture
 
  4.15* Form of Trust Preferred Security (included in Exhibit 4.3)
 
  4.16* Form of Preferred Securities Guarantee Agreement with respect to Trust
         Preferred Securities to be issued by UnionBanCal Finance Trust I
 
  4.17* Form of Preferred Securities Guarantee Agreement with respect to Trust
         Preferred Securities to be issued by UnionBanCal Finance Trust II
 
  4.18* Form of Preferred Securities Guarantee Agreement with respect to Trust
         Preferred Securities to be issued by UnionBanCal Finance Trust III
 
  4.19* Form of Preferred Securities Guarantee Agreement with respect to Trust
         Preferred Securities to be issued by UnionBanCal Finance Trust IV
 
  4.20* Form of Preferred Stock
 
  4.21* Form of Deposit Agreement
 
  4.22* Form of Depositary Share
 
  5.1* Opinion of Skadden, Arps, Slate, Meagher & Flom LLP as to the legality of
         the Common Stock, Preferred Stock, Debt Securities; Trust Preferred
         Securities and Trust Preferred Securities Guarantee
 
 12.1* Statement re: Computation of Ratios of Earnings to Fixed Charges and of
         Earnings to Combined Fixed Charges and Preferred Stock Dividends of UNBC
 
 23.1  Consent of Deloitte & Touche LLP, Independent Auditors
 
 23.2  Consent of Arthur Andersen LLP, Independent Accountants
 
 23.3* Consent of Skadden, Arps, Slate, Meagher & Flom LLP (included in Exhibit
         5.1)
 
 24.1  Power of Attorney of certain officers and directors of UNBC (included on
         signature page)
 
 25.1* Statement of Eligibility on Form T-1 under the Trust Indenture Act of
         1939, as amended, of The First National Bank of Chicago, as Trustee
         under the Indenture
</TABLE>
 
- ------------------------
 
 *  To be filed by amendment or as an exhibit to a document to be incorporated
    or deemed to be incorporated by reference in the Registration Statement.
 
                                      II-2
<PAGE>
ITEM 17.  UNDERTAKINGS
 
    The undersigned registrants hereby undertake:
 
    (1) To file, during any period in which offers or sales are being made, a
post-effective amendment to this registration statement:
 
        (i) To include any prospectus required by Section 10(a)(3) of the
    Securities Act of 1933;
 
        (ii) To reflect in the prospectus any facts or events arising after the
    effective date of the registration statement (or the most recent
    post-effective amendment thereof) which, individually or in the aggregate,
    represent a fundamental change in the information set forth in the
    registration statement. Notwithstanding the foregoing, any increase or
    decrease in volume of securities offered (if the total dollar value of
    securities offered would not exceed that which was registered) and any
    deviation from the low or high end of the estimated maximum offering range
    may be reflected in the form of prospectus filed with the Commission
    pursuant to Rule 424(b) if, in the aggregate, the changes in volume and
    price represent no more than a 20 percentage change in the maximum aggregate
    offering price set forth in the "Calculation of Registration Fee" table in
    the effective registration statement;
 
       (iii) To include any material information with respect to the plan of
    distribution not previously disclosed in the registration statement or any
    material change to such information in the registration statement;
 
PROVIDED, HOWEVER, that paragraphs (1)(i) and 1(ii) do not apply if the
registration statement is on Form S-3 or Form S-8 or Form F-3, and the
information required to be included in a post-effective amendment by those
paragraphs is contained in periodic reports filed with or furnished to the
Commission by the registrants pursuant to Section 13 or Section 15(d) of the
Securities Exchange Act that are incorporated by reference in the registration
statement;
 
    (2) That, for the purpose of determining any liability under the Securities
Act of 1933, each such post-effective amendment shall be deemed to be a new
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof;
 
    (3) To remove from registration by means of a post-effective amendment any
of the securities being registered which remain unsold at the termination of the
offering.
 
    The undersigned registrants hereby undertake that, for purposes of
determining any liability under the Securities Act of 1933, each filing of each
of the registrant's annual report pursuant to Section 13(a) or Section 15(d) of
the Securities Exchange Act that is incorporated by reference in the
registration statement shall be deemed to be a new registration statement
relating to the securities offered herein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.
 
    Insofar as indemnification for liabilities arising under the Securities Act
of 1933 may be permitted to directors, officers and controlling persons of any
of the registrants pursuant to the provisions set forth in Item 15, or
otherwise, each of the registrants has been advised that in the opinion of the
SEC such indemnification is against public policy as expressed in the Act and
is, therefore, unenforceable. In the event that a claim for indemnification
against such liabilities (other than the payment by one of the registrants of
expenses incurred or paid by a director, officer or controlling registrant of
expenses incurred or paid by a director, officer or controlling person of one of
the registrants in the successful defense of any action, suit or proceeding) is
asserted by such director, officer or controlling person in connection with the
securities being registered, each of the registrants will, unless in the opinion
of its counsel the matter has been settled by controlling precedent, submit to a
court of appropriate jurisdiction the question whether such indemnification by
it is against public policy as expressed in the Act and will be governed by the
final adjudication of such issue.
 
                                      II-3
<PAGE>
    The undersigned registrants undertake that:
 
    (1) For purposes of determining any liability under the Securities Act of
1933, the information omitted from the form of prospectus filed as part of this
registration statement in reliance upon Rule 430A and contained in a form of
prospectus filed by the registrant pursuant to Rule 424(b) (1) or (4) or 497(h)
under the Securities Act shall be deemed to be part of this registration
statement as of the time it was declared effective.
 
    (2) For the purpose of determining any liability under the Securities Act of
1933, each post-effective amendment that contains a form of prospectus shall be
deemed to be a new registration statement relating to the securities offered
therein, and the offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.
 
    The undersigned registrants hereby undertake to file an application for the
purpose of determining the eligibility of the trustee to act under subsection
(a) of Section 310 of the Trust Indenture Act in accordance with the rules and
regulations prescribed by the Commission under Section 305(b)(2) of the Act.
 
                                      II-4
<PAGE>
                                   SIGNATURES
 
    Pursuant to the requirements of the Securities Act of 1933, the registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on this Form S-3 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of San Francisco, State of California, on this 18th day
of November, 1998.
 
<TABLE>
<S>                             <C>  <C>
                                UNIONBANCAL CORPORATION
 
                                By:            /s/ TAKAHIRO MORIGUCHI
                                     -----------------------------------------
                                                 Takahiro Moriguchi
                                       PRESIDENT AND CHIEF EXECUTIVE OFFICER
</TABLE>
 
    KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears
below constitutes and appoints Takahiro Moriguchi, Yoshihiko Someya, David I.
Matson and John H. McGuckin, Jr., and each of them, in his or her true and
lawful attorneys-in-fact and agents, each with full power of substitution and
resubstitution, for him or her and in his or her name, place and stead, in any
and all capacities, to sign any and all amendments, including post-effective
amendments, to this Registration Statement, and any registration statement
relating to the offering covered by this Registration Statement and filed
pursuant to Rule 462(b) under the Securities Act of 1933, and to file the same,
with exhibits thereto and other documents in connection therewith, with the
Securities and Exchange Commission, granting unto said attorneys-in-fact and
agents and each of them, full power and authority to do and perform each and
every act and thing requisite and necessary to be done, as fully to all intents
and purposes as he or she might or could do in person, hereby ratifying and
confirming all that each of said attorneys-in-fact and agents of their
substitute or substitutes may lawfully do or cause to be done by virtue hereof.
 
    Pursuant to the requirements of the Securities Act, this Registration
Statement has been signed below by the following persons in the capacities
indicated on November 18, 1998.
 
<TABLE>
<CAPTION>
             SIGNATURES                              TITLE
- ------------------------------------  ------------------------------------
 
<C>                                   <S>
       /s/ TAKAHIRO MORIGUCHI         President and Chief Executive
- ------------------------------------    Officer and Director
         Takahiro Moriguchi             (Principal Executive Officer)
 
        /s/ YOSHIHIKO SOMEYA
- ------------------------------------  Deputy Chairman of the Board
          Yoshihiko Someya
 
        /s/ DAVID I. MATSON           Executive Vice President and Chief
- ------------------------------------    Financial Officer
          David I. Matson               (Principal Financial Officer)
 
       /s/ DAVID A. ANDERSON
- ------------------------------------  Senior Vice President and Controller
         David A. Anderson              (Principal Accounting Officer)
</TABLE>
 
                                      II-5
<PAGE>
<TABLE>
<CAPTION>
             SIGNATURES                              TITLE
- ------------------------------------  ------------------------------------
 
<C>                                   <S>
          /s/ KAORU HAYAMA
- ------------------------------------  Chairman of the Board
            Kaoru Hayama
 
      /s/ RICHARD C. HARTNACK
- ------------------------------------  Vice Chairman of the Board
        Richard C. Hartnack
 
        /s/ ROBERT M. WALKER
- ------------------------------------  Vice Chairman of the Board
          Robert M. Walker
 
       /s/ RICHARD D. FARMAN
- ------------------------------------  Director
         Richard D. Farman
 
       /s/ STANLEY F. FARRAR
- ------------------------------------  Director
         Stanley F. Farrar
 
       /s/ HERMAN E. GALLEGOS
- ------------------------------------  Director
         Herman E. Gallegos
 
        /s/ JACK L. HANCOCK
- ------------------------------------  Director
          Jack L. Hancock
 
          /s/ HARRY W. LOW
- ------------------------------------  Director
            Harry W. Low
 
          /s/ MARY S. METZ
- ------------------------------------  Director
            Mary S. Metz
 
        /s/ RAYMOND E. MILES
- ------------------------------------  Director
          Raymond E. Miles
 
       /s/ J. FERNANDO NIEBLA
- ------------------------------------  Director
         J. Fernando Niebla
</TABLE>
 
                                      II-6
<PAGE>
<TABLE>
<CAPTION>
             SIGNATURES                              TITLE
- ------------------------------------  ------------------------------------
 
<C>                                   <S>
       /s/ SIDNEY R. PETERSEN
- ------------------------------------  Director
         Sidney R. Petersen
 
       /s/ CARL W. ROBERTSON
- ------------------------------------  Director
         Carl W. Robertson
 
        /s/ HENRY T. SWIGERT
- ------------------------------------  Director
          Henry T. Swigert
 
          /s/ TSUNEO WAKAI
- ------------------------------------  Director
            Tsuneo Wakai
 
        /s/ HIROSHI WATANABE
- ------------------------------------  Director
          Hiroshi Watanabe
 
- ------------------------------------  Director
          Blenda J. Wilson
 
- ------------------------------------  Director
          Kenji Yoshizawa
</TABLE>
 
                                      II-7

<PAGE>

                                                                    EXHIBIT 4.2

                                 CERTIFICATE OF TRUST

                                          OF

                             UNIONBANCAL FINANCE TRUST I

          The undersigned, the trustees of UnionBanCal Finance Trust I, desiring
to form a business trust pursuant to Delaware Business Trust Act, 12 DEL. C. 
Section 3810 hereby certify as follows:

          1.   The name of the business trust being formed hereby is UnionBanCal
               Finance Trust I (the "Trust").

          2.   The name and business address of the trustee of the Trust with a
               principal place of business in the State of Delaware is as
               follows:

               First Chicago Delaware Inc.
               300 King Street
               Wilmington, DE  19801

Dated:  November 17, 1998

                                   THE FIRST NATIONAL BANK OF CHICAGO,
                                    as Property Trustee

                                   By:    /s/  Lawrence Dillard       
                                      ---------------------------------
                                        Name:  Lawrence Dillard
                                        Title: First Vice President



                                   FIRST CHICAGO DELAWARE INC., as
                                    Delaware Trustee

                                   By:    /s/   Lawrence Dillard  
                                      ---------------------------------
                                        Name:  Lawrence Dillard
                                        Title: First Vice Presidnet



<PAGE>

                                                                   EXHIBIT 4.3

                                 CERTIFICATE OF TRUST

                                          OF

                             UNIONBANCAL FINANCE TRUST II

          The undersigned, the trustees of UnionBancal Finance Trust II,
desiring to form a business trust pursuant to Delaware Business Trust Act, 12
DEL. C. Section 3810 hereby certify as follows:

          1.   The name of the business trust being formed hereby is UnionBancal
               Finance Trust II (the "Trust").

          2.   The name and business address of the trustee of the Trust with a
               principal place of business in the State of Delaware is as
               follows:

               First Chicago Delaware Inc.
               300 King Street
               Wilmington, DE  19801

Dated:  November 17, 1998

                                   THE FIRST NATIONAL BANK OF CHICAGO,
                                    as Property Trustee

                                   By:   /s/ Lawrence Dillard        
                                      -----------------------------------
                                        Name:  Lawrence Dillard
                                        Title: First Vice President




                                   FIRST CHICAGO DELAWARE INC., as
                                    Delaware Trustee

                                   By:   /s/ Lawrence Dillard  
                                      -----------------------------------
                                        Name:  Lawrence Dillard
                                        Title: First Vice President


<PAGE>

                                                                    EXHIBIT 4.4

                                 CERTIFICATE OF TRUST

                                          OF

                            UNIONBANCAL FINANCE TRUST III

          The undersigned, the trustees of UnionBanCal Finance Trust III,
desiring to form a business trust pursuant to Delaware Business Trust Act, 12
DEL. C. Section 3810 hereby certify as follows:

          1.   The name of the business trust being formed hereby is UnionBanCal
               Finance Trust III (the "Trust").

          2.   The name and business address of the trustee of the Trust with a
               principal place of business in the State of Delaware is as
               follows:

               First Chicago Delaware Inc.
               300 King Street
               Wilmington, DE  19801

Dated:  November 17, 1998

                                   THE FIRST NATIONAL BANK OF CHICAGO,
                                    as Property Trustee

                                   By:    /s/ Lawrence Dillard 
                                      -----------------------------------
                                        Name:  Lawrence Dillard
                                        Title: First Vice President




                                   FIRST CHICAGO DELAWARE INC., as
                                    Delaware Trustee

                                   By:    /s/ Lawrence Dillard  
                                      -----------------------------------
                                        Name:  Lawrence Dillard
                                        Title: First Vice President

<PAGE>

                                                                   EXHIBIT 4.5


                                 CERTIFICATE OF TRUST

                                          OF

                             UNIONBANCAL FINANCE TRUST IV

          The undersigned, the trustees of UnionBanCal Finance Trust IV,
desiring to form a business trust pursuant to Delaware Business Trust Act, 12
DEL. C. Section 3810 hereby certify as follows:

          1.   The name of the business trust being formed hereby is UnionBanCal
               Finance Trust IV (the "Trust").

          2.   The name and business address of the trustee of the Trust with a
               principal place of business in the State of Delaware is as
               follows:

               First Chicago Delaware Inc.
               300 King Street
               Wilmington, DE  19801

Dated:  November 17, 1998

                                   THE FIRST NATIONAL BANK OF CHICAGO,
                                    as Property Trustee

                                   By:    /s/ Lawrence Dillard 
                                      -----------------------------------
                                        Name:  Lawrence Dillard
                                        Title: First Vice President



                                   FIRST CHICAGO DELAWARE INC., as
                                    Delaware Trustee
     
                                   By:    /s/ Lawrence Dillard 
                                      -----------------------------------
                                        Name:  Lawrence Dillard
                                        Title: First Vice President



<PAGE>
                                                                    EXHIBIT 23.1
 
INDEPENDENT AUDITORS' CONSENT
 
We consent to the incorporation by reference in this Registration Statement of
UnionBanCal Corporation on Form S-3 of our report dated January 30, 1998
(November 18, 1998 as to the exchange of common stock referred to in Note 1,
paragraphs 3 and 4, the adoption of SFAS No. 130, "Reporting Comprehensive
Income," referred to in Notes 1 and 18, and the stock split referred to in Note
23), appearing in the Annual Report on Form 10-K/A of UnionBanCal Corporation
for the year ended December 31, 1997, and to the reference to us under the
heading "Experts" in the Prospectus, which is part of this Registration
Statement.
 
DELOITTE & TOUCHE LLP
San Francisco, California
November 19, 1998

<PAGE>
                                                                    EXHIBIT 23.2
 
                   CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS
 
As independent public accountants, we hereby consent to the incorporation by
reference of our report dated January 24, 1996 on the consolidated financial
statements of Union Bank and subsidiaries for the year ended December 31, 1995
(not presented herein), included in the Annual Report on Form 10-K/A of
UnionBanCal Corporation and subsidiaries, in this Form S-3 Registration
Statement. It should be noted that we have not audited any financial statements
of Union Bank and subsidiaries subsequent to December 31, 1995 or performed any
audit procedures subsequent to the date of our report.
 
                                          ARTHUR ANDERSEN LLP
 
San Francisco, California
November 16, 1998


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