<PAGE>
 
          As filed with the Securities and Exchange Commission on August 7, 1997
                                                      Registration No. 333-_____

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
                            -----------------------

                                    FORM S-8
            REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
                            -----------------------

                          NATIONAL MERCANTILE BANCORP
             (Exact name of registrant as specified in its charter)

          CALIFORNIA                                             95-3819685
(State or other jurisdiction of                               (I.R.S. Employer
 incorporation or organization)                              Identification No.)

                            1840 CENTURY PARK EAST
                         LOS ANGELES, CALIFORNIA 90067
             (Address of Principal Executive Offices and Zip Code)

                            -----------------------

               NATIONAL MERCANTILE BANCORP 1990 STOCK OPTION PLAN
                              (Full Title of Plan)

                            -----------------------

                              SCOTT A. MONTGOMERY
                     PRESIDENT AND CHIEF EXECUTIVE OFFICER
                          NATIONAL MERCANTILE BANCORP
                             1840 CENTURY PARK EAST
                         LOS ANGELES, CALIFORNIA 90067
                    (Name and address of agent for service)

                                 (310) 277-2265
         (Telephone number, including area code, of agent for service)

                                WITH A COPY TO:
                                THOMAS D. PHELPS
                         MANATT, PHELPS & PHILLIPS, LLP
                          11355 WEST OLYMPIC BOULEVARD
                         LOS ANGELES, CALIFORNIA 90064

                        Calculation of Registration Fee
<TABLE>
<CAPTION>
========================================================================================================
                                             Proposed Maximum      Proposed Maximum
  Title of Securities      Amount to be       Offering Price           Aggregate           Amount of
   to be Registered        Registered(1)       per Share(2)        Offering Price(2)    Registration Fee
 <S>                       <C>               <C>                   <C>                  <C>
--------------------------------------------------------------------------------------------------------
 Common Stock, no par        22,003(3)        $ 13.00                $ 286,039            $ 87.00             
 value
========================================================================================================
</TABLE>

(1)      This Registration Statement covers, in addition to the number of shares
         of Common Stock stated above, such indeterminate number of shares of
         Common Stock as may be issued upon exercise of options granted under
         the Registrant's 1990 Stock Option Plan as a result of adjustment
         provisions thereto.
(2)      Estimated solely for purposes of calculating the amount of the
         registration fee pursuant to Rule 457, based upon the average of the
         high and low prices of the Common Stock as reported on the Nasdaq
         SmallCap Market System on July 31, 1997.
(3)      Adjusted to reflect a 9.09 to 1 reverse stock split effected by the
         Company on June 20, 1997.

================================================================================
<PAGE>
 
         Unless otherwise indicated, all information contained in this
 Registration Statement reflects a 9.09 to 1 reverse stock split effected by the
 Company on June 20, 1997.

                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS


         The following documents listed under this Part I and the documents
incorporated by reference under Item 3 of Part II to this Form S-8, taken
together, constitute a prospectus that meets the requirements of Section 10(a)
of the Securities Act of 1933, as amended (the "Securities Act"), and are
incorporated herein by reference.


Item 1.  Plan Information
         ----------------

         (a)    National Mercantile Bancorp 1990 Stock Option Plan
         (b)    Prospectus for the 1990 Stock Option Plan
         (c)    Form of Nonqualified Stock Option Agreement
         (d)    Form of Incentive Stock Option Agreement

Item 2.  Registrant Information and Employee Plan Annual Information
         -----------------------------------------------------------

         The written statement required to be provided to participants pursuant
to this Item 2 is set forth in the Prospectus referred to in Item 1 above.




                                      I-1

<PAGE>
 
                                    PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT


         National Mercantile Bancorp (the "Registrant") hereby files this
Registration Statement on Form S-8 with the Securities and Exchange Commission
(the "Commission") to register 22,003 shares of the Registrant's common stock,
no par value (the "Common Stock") for issuance pursuant to the Registrant's 1990
Stock Option Plan (the "Plan"), and such indeterminate number of shares as may
become available under the Plan as a result of the adjustment provisions
thereof.


Item 3.  Incorporation of Documents by Reference
         ---------------------------------------

         The following documents previously filed by the Registrant with the
Commission pursuant to the Securities Exchange Act of 1934, as amended (the
"Exchange Act") are incorporated herein by reference:

         (a)    The Registrant's Annual Report on Form 10-K for the fiscal year
                ended December 31, 1996 filed pursuant to Section 13(a) or 15(d)
                of the Exchange Act;

         (b)    All other reports filed by the Registrant pursuant to Section
                13(a) or 15(d) of the Exchange Act since the end of the latest
                fiscal year covered by the Annual Report referred to in (a)
                above; and

         (c)    The description of the Common Stock set forth on pages 7, 8 and
                9 of the Company's Amendment No. 2 to its Registration Statement
                on Form S-14 (Registration No. 2-82386) filed under the
                Securities Act, which description was incorporated by reference
                in the Company's Registration Statement on Form 8-A, dated June
                15, 1987, filed under Section 12 of the Exchange Act, and
                including any amendments or reports filed for the purpose of
                updating such description.

         All documents filed by the Registrant pursuant to Sections 13(a),
13(c), 14 and 15(d) of the Exchange Act subsequent to the date of this
Registration Statement and prior to the filing of a post-effective amendment
which indicates that all securities offered hereby have been sold or which
deregisters all securities then remaining unsold shall be deemed to be
incorporated herein by reference and to be a part hereof from the date of filing
of such documents.

         Any statement made in a document incorporated or deemed to be
incorporated by reference herein shall be deemed to be modified or superseded
for purposes of this Registration Statement to the extent that a statement
contained herein or in any other subsequently filed document which is also
incorporated or deemed to be incorporated by reference herein modifies or
supersedes such statement. Any such statement so modified or superseded shall
not be deemed, except as so modified or superseded, to constitute a part of this
Registration Statement.

                                      II-1
<PAGE>
 
Item 4.  Description of Securities
         -------------------------

         Not applicable.

Item 5.  Interests of Named Experts and Counsel
         --------------------------------------

         Not applicable.

Item 6.  Indemnification of Directors and Officers
         -----------------------------------------

         Section 317 of the General Corporation Law of the State of California
(the "GCL") and Article V of the Registrant's Bylaws provide for the
indemnification of directors and officers under certain circumstances. The
Registrant's Bylaws grant the Registrant the power to indemnify its directors
and officers under certain circumstances to the extent permitted by the GCL
against certain expenses, judgments, fines, settlements, and other amounts
actually and reasonably incurred in connection with any proceeding arising by
reason of such person's position as a director or officer of the Registrant.
Pursuant to the GCL and the Registrant's Bylaws, the Registrant is required to
indemnify directors and officers against expenses actually and reasonably
incurred to the extent that such party is successful on the merits in the
defense of certain proceedings.

         Section 204(a)(11) of the GCL provides for the indemnification, subject
to certain limitations, of directors and officers for breach of their duty to a
corporation and its stockholders in excess of that expressly permitted by
Section 317 of the GCL. An amendment to the Articles of Incorporation of the
Registrant adopted the implementation of Section 204(a)(11) of the GCL.

         In addition, the Registrant has entered into Indemnity Agreements with
certain of its directors and certain officers which provide for, among other
items and except to the extent prohibited by any limitations on indemnification
under the GCL which cannot be waived, the mandatory indemnification by the
Registrant of any amount which a director or officer is legally obligated to pay
because of claims made against such person relating to his service as a director
or officer of the Registrant.

         The Registrant also maintains a directors' and officers' liability
insurance policy insuring the Registrant's directors and officers against
certain liabilities and expenses incurred by them in their capacities as such,
and insuring the Registrant under certain circumstances, in the event that
indemnification payments are made by the Registrant to such directors and
officers.

Item 7.  Exemption from Registration Claimed
         -----------------------------------

         Not applicable.

                                      II-2
<PAGE>
 
Item 8.  Exhibits
         --------                               
<TABLE> 
<CAPTION> 
         Exhibit      
         Number      Description
         -------     -----------
         <C>         <S> 
         5.1         Opinion of Manatt, Phelps & Phillips, LLP

         23.1        Consent of Manatt, Phelps & Phillips, LLP (see Exhibit 5.1)

         23.2        Consent of Deloitte & Touche LLP

         24.1        Power of Attorney (see page II-5)

         99.1        National Mercantile Bancorp 1990 Stock Option Plan

         99.2        Form of Nonqualified Stock Option Agreement
 
         99.3        Form of Incentive Stock Option Agreement
</TABLE>

Item 9.  Undertakings
         ------------

         (a)    The undersigned Registrant hereby undertakes:

                (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;

                       (ii)   To reflect in the Prospectus any facts or events
                              arising after the effective date of this
                              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 this
                              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) of the
                              Securities Act if, in the aggregate, the changes
                              in volume and price represent no more than a 20%
                              change in the maximum aggregate offering price set
                              forth in the "Calculation of Registration Fee"
                              table in the effective Registration Statement; and

                       (iii)  To include any material information with respect
                              to the plan of distribution not previously
                              disclosed in this Registration Statement or any
                              material change to such information in this
                              Registration Statement;

                Provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do
not apply if the information required to be included in the post-effective
amendment by those paragraphs is contained in periodic reports filed with or
furnished to the Commission by the Registrant pursuant to Section 13 or Section
15(d) of the Exchange Act that are incorporated by reference in this
Registration Statement.

                                      II-3
<PAGE>
 
                (2)    That, for the purpose of determining any liability under
the Securities Act, 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.

         (b)    The undersigned Registrant hereby undertakes that, for purposes
of determining any liability under the Securities Act, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act (and, where applicable, each filing of an employee benefit plan's
annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in this Registration Statement 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.

         (c)    Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the Registrant pursuant to the foregoing provisions, or otherwise, the
Registrant has been advised that in the opinion of the Commission such
indemnification is against public policy as expressed in the Securities Act and
is, therefore, unenforceable. In the event that a claim for indemnification
against such liabilities (other than the payment by the Registrant of expenses
incurred or paid by a director, officer or controlling person of the Registrant
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, the Registrant 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 Securities Act and will be governed by the final
adjudication of such issue.

         (d)    The undersigned Registrant hereby undertakes to deliver or cause
to be delivered with the Prospectus, to each person to whom the Prospectus is
sent or given, the latest annual report to security holders that is incorporated
by reference in the Prospectus and furnished pursuant to and meeting the
requirements of Rule 14a-3 or Rule 14c-3 under the Exchange Act; and, where
interim financial information required to be presented by Article 3 of
Regulation S-X are not set forth in the Prospectus, to deliver, or cause to be
delivered to each person to whom the Prospectus is sent or given, the latest
quarterly report that is specifically incorporated by reference in the
Prospectus to provide such interim financial information.

                                      II-4
<PAGE>
 
                                   SIGNATURES

         Pursuant to the requirements of the Securities Act, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Los Angeles, State of California, on this 7th day of
August, 1997.

                         NATIONAL MERCANTILE BANCORP


                         By /s/ Scott A. Montgomery
                            --------------------------
                            Scott A. Montgomery
                            President and Chief Executive Officer

                         By /s/ Joseph W. Kiley III
                            --------------------------
                            Joseph W. Kiley III
                            Executive Vice President and Chief Financial Officer


         KNOW ALL MEN BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints each of Scott A. Montgomery and Joseph W.
Kiley III his true and lawful attorney-in-fact and agent, each with full power
of substitution, for him and in his name, place and stead, in any and all
capacities, to sign any or all amendments to this Registration Statement, and to
file the same with all exhibits thereto, and all other documents in connection
therewith, with the Commission, granting unto each said attorney-in-fact and
agent with full power and authority to do and perform each and every act and
thing requisite and necessary to be done in and about the premises, as fully to
all intents and purposes as he might or could do in person, hereby ratifying and
confirming all that each said attorney-in-fact and agent, or his substitute, may
lawfully do or cause to be done by virtue hereof.

         Pursuant to the requirements of the Securities Act, as amended, this
Registration Statement has been signed by the following persons in the
capacities and on the date indicated.

<TABLE>
<CAPTION> 
Signature                    Title                           Date
---------                    -----                           ----
<S>                          <C>                             <C> 

/s/ Robert E. Gipson         Chairman                        August 7, 1997 
--------------------------
Robert E. Gipson
 
/s/ Alan Grahm               Secretary, Director             August 7, 1997 
--------------------------
Alan Grahm
 
/s/ Joseph W. Kiley III      Executive Vice President,       August 7, 1997 
--------------------------   Chief Financial Officer and 
Joseph W. Kiley III          Director
 
/s/ Scott A. Montgomery      President, Chief Executive      August 7, 1997 
--------------------------   Officer and Director
Scott A. Montgomery          
 
/s/ Robert E. Thomson        Vice Chair                      August 7, 1997 
--------------------------
Robert E. Thomson
</TABLE>

                                      II-5
<PAGE>
 
                          NATIONAL MERCANTILE BANCORP
                                    FORM S-8

                                 EXHIBIT INDEX

<TABLE>
<CAPTION> 
EXHIBIT
NUMBER
<C>          <S>

5.1          Opinion of Manatt, Phelps & Phillips, LLP

23.1         Consent of Manatt, Phelps & Phillips, LLP (see Exhibit 5.1)

23.2         Consent of Deloitte & Touche LLP

24.1         Power of Attorney (see page II-5)

99.1         National Mercantile Bancorp 1990 Stock Option Plan

99.2         Form of Nonqualified Stock Option Agreement
 
99.3         Form of Incentive Stock Option Agreement 
</TABLE>

                                      II-6
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 20860}]
{"company-data": {"conformed-name": "NATIONAL MERCANTILE BANCORP", "cik": "0000714801", "assigned-sic": "6022", "irs-number": "953819685", "state-of-incorporation": "CA", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-33139", "film-number": "97653445"}, "business-address": {"street1": "1840 CENTURY PARK EAST", "city": "LOS ANGELES", "state": "CA", "zip": "90067", "phone": "3102772265"}, "mail-address": {"street1": "1840 CENTURY PARK EAST", "city": "LOS ANGELES", "state": "CA", "zip": "90067"}}
As filed with the Securities and Exchange Commission on August 7, 1997
                                                      Registration No. 333-_____

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
                            -----------------------

                                    FORM S-8
            REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
                            -----------------------

                          NATIONAL MERCANTILE BANCORP
             (Exact name of registrant as specified in its charter)

          CALIFORNIA                                             95-3819685
(State or other jurisdiction of                               (I.R.S. Employer
 incorporation or organization)                              Identification No.)

                            1840 CENTURY PARK EAST
                         LOS ANGELES, CALIFORNIA 90067
             (Address of Principal Executive Offices and Zip Code)

                            -----------------------

               NATIONAL MERCANTILE BANCORP 1990 STOCK OPTION PLAN
                              (Full Title of Plan)

                            -----------------------

                              SCOTT A. MONTGOMERY
                     PRESIDENT AND CHIEF EXECUTIVE OFFICER
                          NATIONAL MERCANTILE BANCORP
                             1840 CENTURY PARK EAST
                         LOS ANGELES, CALIFORNIA 90067
                    (Name and address of agent for service)

                                 (310) 277-2265
         (Telephone number, including area code, of agent for service)

                                WITH A COPY TO:
                                THOMAS D. PHELPS
                         MANATT, PHELPS & PHILLIPS, LLP
                          11355 WEST OLYMPIC BOULEVARD
                         LOS ANGELES, CALIFORNIA 90064

                        Calculation of Registration Fee
========================================================================================================
                                             Proposed Maximum      Proposed Maximum
  Title of Securities      Amount to be       Offering Price           Aggregate           Amount of
   to be Registered        Registered(1)       per Share(2)        Offering Price(2)    Registration Fee
--------------------------------------------------------------------------------------------------------
 Common Stock, no par        22,003(3)        $ 13.00                $ 286,039            $ 87.00             
 value
========================================================================================================
(1)      This Registration Statement covers, in addition to the number of shares
         of Common Stock stated above, such indeterminate number of shares of
         Common Stock as may be issued upon exercise of options granted under
         the Registrant's 1990 Stock Option Plan as a result of adjustment
         provisions thereto.
(2)      Estimated solely for purposes of calculating the amount of the
         registration fee pursuant to Rule 457, based upon the average of the
         high and low prices of the Common Stock as reported on the Nasdaq
         SmallCap Market System on July 31, 1997.
(3)      Adjusted to reflect a 9.09 to 1 reverse stock split effected by the
         Company on June 20, 1997.

================================================================================
Unless otherwise indicated, all information contained in this
 Registration Statement reflects a 9.09 to 1 reverse stock split effected by the
 Company on June 20, 1997.

                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

         The following documents listed under this Part I and the documents
incorporated by reference under Item 3 of Part II to this Form S-8, taken
together, constitute a prospectus that meets the requirements of Section 10(a)
of the Securities Act of 1933, as amended (the "Securities Act"), and are
incorporated herein by reference.

Item 1.  Plan Information
         ----------------

         (a)    National Mercantile Bancorp 1990 Stock Option Plan
         (b)    Prospectus for the 1990 Stock Option Plan
         (c)    Form of Nonqualified Stock Option Agreement
         (d)    Form of Incentive Stock Option Agreement

Item 2.  Registrant Information and Employee Plan Annual Information
         -----------------------------------------------------------

         The written statement required to be provided to participants pursuant
to this Item 2 is set forth in the Prospectus referred to in Item 1 above.

                                      I-1
PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

         National Mercantile Bancorp (the "Registrant") hereby files this
Registration Statement on Form S-8 with the Securities and Exchange Commission
(the "Commission") to register 22,003 shares of the Registrant's common stock,
no par value (the "Common Stock") for issuance pursuant to the Registrant's 1990
Stock Option Plan (the "Plan"), and such indeterminate number of shares as may
become available under the Plan as a result of the adjustment provisions
thereof.

Item 3.  Incorporation of Documents by Reference
         ---------------------------------------

         The following documents previously filed by the Registrant with the
Commission pursuant to the Securities Exchange Act of 1934, as amended (the
"Exchange Act") are incorporated herein by reference:

         (a)    The Registrant's Annual Report on Form 10-K for the fiscal year
                ended December 31, 1996 filed pursuant to Section 13(a) or 15(d)
                of the Exchange Act;

         (b)    All other reports filed by the Registrant pursuant to Section
                13(a) or 15(d) of the Exchange Act since the end of the latest
                fiscal year covered by the Annual Report referred to in (a)
                above; and

         (c)    The description of the Common Stock set forth on pages 7, 8 and
                9 of the Company's Amendment No. 2 to its Registration Statement
                on Form S-14 (Registration No. 2-82386) filed under the
                Securities Act, which description was incorporated by reference
                in the Company's Registration Statement on Form 8-A, dated June
                15, 1987, filed under Section 12 of the Exchange Act, and
                including any amendments or reports filed for the purpose of
                updating such description.

         All documents filed by the Registrant pursuant to Sections 13(a),
13(c), 14 and 15(d) of the Exchange Act subsequent to the date of this
Registration Statement and prior to the filing of a post-effective amendment
which indicates that all securities offered hereby have been sold or which
deregisters all securities then remaining unsold shall be deemed to be
incorporated herein by reference and to be a part hereof from the date of filing
of such documents.

         Any statement made in a document incorporated or deemed to be
incorporated by reference herein shall be deemed to be modified or superseded
for purposes of this Registration Statement to the extent that a statement
contained herein or in any other subsequently filed document which is also
incorporated or deemed to be incorporated by reference herein modifies or
supersedes such statement. Any such statement so modified or superseded shall
not be deemed, except as so modified or superseded, to constitute a part of this
Registration Statement.

                                      II-1
Item 4.  Description of Securities
         -------------------------

         Not applicable.

Item 5.  Interests of Named Experts and Counsel
         --------------------------------------

         Not applicable.

Item 6.  Indemnification of Directors and Officers
         -----------------------------------------

         Section 317 of the General Corporation Law of the State of California
(the "GCL") and Article V of the Registrant's Bylaws provide for the
indemnification of directors and officers under certain circumstances. The
Registrant's Bylaws grant the Registrant the power to indemnify its directors
and officers under certain circumstances to the extent permitted by the GCL
against certain expenses, judgments, fines, settlements, and other amounts
actually and reasonably incurred in connection with any proceeding arising by
reason of such person's position as a director or officer of the Registrant.
Pursuant to the GCL and the Registrant's Bylaws, the Registrant is required to
indemnify directors and officers against expenses actually and reasonably
incurred to the extent that such party is successful on the merits in the
defense of certain proceedings.

         Section 204(a)(11) of the GCL provides for the indemnification, subject
to certain limitations, of directors and officers for breach of their duty to a
corporation and its stockholders in excess of that expressly permitted by
Section 317 of the GCL. An amendment to the Articles of Incorporation of the
Registrant adopted the implementation of Section 204(a)(11) of the GCL.

         In addition, the Registrant has entered into Indemnity Agreements with
certain of its directors and certain officers which provide for, among other
items and except to the extent prohibited by any limitations on indemnification
under the GCL which cannot be waived, the mandatory indemnification by the
Registrant of any amount which a director or officer is legally obligated to pay
because of claims made against such person relating to his service as a director
or officer of the Registrant.

         The Registrant also maintains a directors' and officers' liability
insurance policy insuring the Registrant's directors and officers against
certain liabilities and expenses incurred by them in their capacities as such,
and insuring the Registrant under certain circumstances, in the event that
indemnification payments are made by the Registrant to such directors and
officers.

Item 7.  Exemption from Registration Claimed
         -----------------------------------

         Not applicable.

                                      II-2
Item 8.  Exhibits
         --------
Exhibit      
         Number      Description
         -------     -----------
5.1         Opinion of Manatt, Phelps & Phillips, LLP

         23.1        Consent of Manatt, Phelps & Phillips, LLP (see Exhibit 5.1)

         23.2        Consent of Deloitte & Touche LLP

         24.1        Power of Attorney (see page II-5)

         99.1        National Mercantile Bancorp 1990 Stock Option Plan

         99.2        Form of Nonqualified Stock Option Agreement
 
         99.3        Form of Incentive Stock Option Agreement
Item 9.  Undertakings
         ------------

         (a)    The undersigned Registrant hereby undertakes:

                (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;

                       (ii)   To reflect in the Prospectus any facts or events
                              arising after the effective date of this
                              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 this
                              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) of the
                              Securities Act if, in the aggregate, the changes
                              in volume and price represent no more than a 20%
                              change in the maximum aggregate offering price set
                              forth in the "Calculation of Registration Fee"
                              table in the effective Registration Statement; and

                       (iii)  To include any material information with respect
                              to the plan of distribution not previously
                              disclosed in this Registration Statement or any
                              material change to such information in this
                              Registration Statement;

                Provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do
not apply if the information required to be included in the post-effective
amendment by those paragraphs is contained in periodic reports filed with or
furnished to the Commission by the Registrant pursuant to Section 13 or Section
15(d) of the Exchange Act that are incorporated by reference in this
Registration Statement.

                                      II-3
(2)    That, for the purpose of determining any liability under
the Securities Act, 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.

         (b)    The undersigned Registrant hereby undertakes that, for purposes
of determining any liability under the Securities Act, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act (and, where applicable, each filing of an employee benefit plan's
annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in this Registration Statement 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.

         (c)    Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the Registrant pursuant to the foregoing provisions, or otherwise, the
Registrant has been advised that in the opinion of the Commission such
indemnification is against public policy as expressed in the Securities Act and
is, therefore, unenforceable. In the event that a claim for indemnification
against such liabilities (other than the payment by the Registrant of expenses
incurred or paid by a director, officer or controlling person of the Registrant
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, the Registrant 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 Securities Act and will be governed by the final
adjudication of such issue.

         (d)    The undersigned Registrant hereby undertakes to deliver or cause
to be delivered with the Prospectus, to each person to whom the Prospectus is
sent or given, the latest annual report to security holders that is incorporated
by reference in the Prospectus and furnished pursuant to and meeting the
requirements of Rule 14a-3 or Rule 14c-3 under the Exchange Act; and, where
interim financial information required to be presented by Article 3 of
Regulation S-X are not set forth in the Prospectus, to deliver, or cause to be
delivered to each person to whom the Prospectus is sent or given, the latest
quarterly report that is specifically incorporated by reference in the
Prospectus to provide such interim financial information.

                                      II-4
SIGNATURES

         Pursuant to the requirements of the Securities Act, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Los Angeles, State of California, on this 7th day of
August, 1997.

                         NATIONAL MERCANTILE BANCORP

                         By /s/ Scott A. Montgomery
                            --------------------------
                            Scott A. Montgomery
                            President and Chief Executive Officer

                         By /s/ Joseph W. Kiley III
                            --------------------------
                            Joseph W. Kiley III
                            Executive Vice President and Chief Financial Officer

         KNOW ALL MEN BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints each of Scott A. Montgomery and Joseph W.
Kiley III his true and lawful attorney-in-fact and agent, each with full power
of substitution, for him and in his name, place and stead, in any and all
capacities, to sign any or all amendments to this Registration Statement, and to
file the same with all exhibits thereto, and all other documents in connection
therewith, with the Commission, granting unto each said attorney-in-fact and
agent with full power and authority to do and perform each and every act and
thing requisite and necessary to be done in and about the premises, as fully to
all intents and purposes as he might or could do in person, hereby ratifying and
confirming all that each said attorney-in-fact and agent, or his substitute, may
lawfully do or cause to be done by virtue hereof.

         Pursuant to the requirements of the Securities Act, as amended, this
Registration Statement has been signed by the following persons in the
capacities and on the date indicated.
Signature                    Title                           Date
---------                    -----                           ----
/s/ Robert E. Gipson         Chairman                        August 7, 1997 
--------------------------
Robert E. Gipson
 
/s/ Alan Grahm               Secretary, Director             August 7, 1997 
--------------------------
Alan Grahm
 
/s/ Joseph W. Kiley III      Executive Vice President,       August 7, 1997 
--------------------------   Chief Financial Officer and 
Joseph W. Kiley III          Director
 
/s/ Scott A. Montgomery      President, Chief Executive      August 7, 1997 
--------------------------   Officer and Director
Scott A. Montgomery          
 
/s/ Robert E. Thomson        Vice Chair                      August 7, 1997 
--------------------------
Robert E. Thomson
II-5
NATIONAL MERCANTILE BANCORP
                                    FORM S-8

                                 EXHIBIT INDEX
EXHIBIT
NUMBER
5.1          Opinion of Manatt, Phelps & Phillips, LLP

23.1         Consent of Manatt, Phelps & Phillips, LLP (see Exhibit 5.1)

23.2         Consent of Deloitte & Touche LLP

24.1         Power of Attorney (see page II-5)

99.1         National Mercantile Bancorp 1990 Stock Option Plan

99.2         Form of Nonqualified Stock Option Agreement
 
99.3         Form of Incentive Stock Option Agreement
II-6