<PAGE>

    As filed with the Securities and Exchange Commission on March 19, 2001

                                                  REGISTRATION NO. 333-_________
================================================================================

                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
                              --------------------
                                    FORM S-8
            REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
                                   __________

                          PROSPERITY BANCSHARES, INC.
             (Exact name of registrant as specified in its charter)

            TEXAS                                            74-2331986
(State or other jurisdiction of                           (I.R.S. Employer
incorporation or organization)                           Identification No.)
                             ---------------------
                                4295 SAN FELIPE
                              HOUSTON, TEXAS 77027
                                 (713) 693-9300
          (Address of Principal Executive Offices Including Zip Code)

                             ---------------------
   COMMERCIAL BANCSHARES, INC. INCENTIVE STOCK OPTION PLAN FOR KEY EMPLOYEES
                             (Full title of Plan)
                             ---------------------
                                  DAVID ZALMAN
                          PROSPERITY BANCSHARES, INC.
                                4295 SAN FELIPE
                              HOUSTON, TEXAS 77027
                    (Name and address of agent for service)

                                 (713) 693-9300
         (Telephone number, including area code, of agent for service)

                                    Copy to:

                              WILLIAM T. LUEDKE IV
                         BRACEWELL & PATTERSON, L.L.P.
                           SOUTH TOWER PENNZOIL PLACE
                        711 LOUISIANA STREET, SUITE 2900
                           HOUSTON, TEXAS 77002-2781
                                 (713) 223-2900
                                  ____________
                        CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>
                                                PROPOSED MAXIMUM          PROPOSED MAXIMUM       AMOUNT OF
 TITLE OF SECURITIES       AMOUNT TO BE          OFFERING PRICE          AGGREGATE OFFERING     REGISTRATION
   TO BE REGISTERED       REGISTERED(1)      PER SHARE(1)(2)(3)(4)       PRICE(1)(2)(3)(4)          FEE
<S>                      <C>                <C>                        <C>                      <C>
Common Stock,             12,090 shares             $ 1.45(3)                  $56,026             $14.00
$1.00 par value                                     $10.32(4)
----------------------
</TABLE>

(1)       This Registration Statement shall also include any additional shares
          of Common Stock which may be offered and  issued pursuant to the
          antidilution provisions of the Plan.
(2)       Estimated solely for purposes of calculating the registration fee in
          accordance with Rule 457(h).
(3)       7,750 shares under the Plan are valued at an exercise price of $1.45
          pursuant to options to acquire such shares which are outstanding under
          the plan.
(4)       4,340 shares under the Plan are valued at an exercise price of $10.32
          pursuant to options to acquire such shares which are outstanding under
          the Plan.
<PAGE>

                                    PART I

             INFORMATION REQUIRED IN THE SECTION 10(A) PROSPECTUS

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

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

*         The information required by Items 1 and 2 of Part I of Form S-8 is
          omitted from this Registration Statement in accordance with the Note
          to Part 1 of Form S-8 and Rule 428 promulgated under the Securities
          Act of 1933, as amended (the "Securities Act").
<PAGE>

                                    PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

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

     The following documents filed by Prosperity Bancshares, Inc., a Texas
corporation (the "Company"), (Commission File No. 000-25051) with the Securities
and Exchange Commission (the "Commission") are incorporated by reference into
this Registration Statement as of their respective dates:

          1.  The Company's Annual Report on Form 10-K for the year ended
     December 31, 2000;

          2.  The Company's Current Report on Form 8-K under Item 2 dated March
     1, 2001; and

          3.  The description of the common stock, par value $1.00 per share,
     contained in the Company's Registration Statement on Form 8-A, dated
     November 10, 1998.

     All documents filed by the Company pursuant to Sections 13(a), 13(c), 14
and 15(d) of the Securities Exchange Act of 1934, as amended (the "Exchange
Act"), after the date of this Registration Statement and prior to the filing of
a post-effective amendment hereto which indicates that all securities offered
have been sold or which deregisters all such securities then remaining unsold,
shall be deemed to be incorporated herein by reference and to be a part hereof
from the date of filing such documents.  Any statement contained herein or in
any 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 in any other subsequently
filed document which also is or is deemed to be incorporated by reference herein
modifies or supersedes such statement.  Any such statement so modified or
superseded shall not be deemed to constitute a part of this Registration
Statement, except as so modified or superseded.

Item 4.   Description of Securities.
          -------------------------

     Not applicable.

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

     Not applicable.

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

     The Registrant's Amended and Restated Articles of Incorporation (the
"Articles of Incorporation") and Amended and Restated Bylaws ("Bylaws") require
the Registrant to indemnify officers and directors of the Registrant to the
fullest extent permitted by Article 2.02-1 of the Texas Business Corporation Act
("TBCA") of the State of Texas.  Generally, Article 2.02-1 of the TBCA permits a
corporation to indemnify a person who was, is, or is threatened to be a named
defendant or respondent in a proceeding because the person was or is a director
or officer if it is determined that such person (i) conducted himself in good
faith, (ii) reasonably believed (a) in the case of conduct in his official
capacity as a director or officer of the corporation, that his conduct was in
the corporation's best interests or (b) in the case of other situations, that
his conduct was at least not opposed to the corporation's best interests and
(iii) in the case of any criminal proceeding, had no reasonable cause to believe
that his conduct was unlawful.  In addition, the TBCA requires a corporation to
indemnify a director or officer for any action that such director or officer is
wholly successful in defending on the merits.

                                      II-1
<PAGE>

     The Company's Articles of Incorporation provide that a director of the
Company will not be liable to the corporation for monetary damages for an act or
omission in the director's capacity as a director, except to the extent not
permitted by law.  Texas law does not permit exculpation of liability in the
case of (i) a breach of the director's duty of loyalty to the corporation or its
shareholders, (ii) an act or omission not in good faith that involves
intentional misconduct or a knowing violation of the law, (iii) a transaction
from which a director received an improper benefit, whether or not the benefit
resulted from an action taken within the scope of the director's office or (iv)
an act or omission for which the liability of the director is expressly provided
by statute.

     The Company may provide liability insurance for each director and officer
for certain losses  arising from claims or charges made against them while
acting in their capabilities as directors or officers of the Company, whether or
not the Registrant would have the power to indemnify such person against such
liability, as permitted by law.

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

          Not applicable.

Item 8.   Exhibits.
          ---------

<TABLE>
<C>     <S>
  4.1   Form of certificate representing shares of Prosperity common stock (incorporated
        herein by reference to Exhibit 4 to the Company's Registration Statement on Form S-1
        (Registration No. 333-63267)).
  4.2   Form of Indenture by and between Prosperity Bancshares, Inc. and First Union Trust
        Company, National Association with respect to the Junior Subordinated Debentures of
        Prosperity Bancshares, Inc. (incorporated by reference from Exhibit 4.1 to the
        Company's Registration Statement on Form S-1 (Registration No. 333-89481)).
  4.3   Form of Amended and Restated Trust Agreement of Prosperity Capital Trust I
        (incorporated by reference from Exhibit 4.5 to the Company's Registration Statement
        on Form S-1 (Registration No. 333-89481).
  4.4   Form of Trust Preferred Securities Guarantee Agreement by and between Prosperity
        Bancshares, Inc. and First Union Trust Company, National Association (incorporated
        by reference from Exhibit 4.7 to the Company's Registration Statement on Form S-1
        Registration No. 333-89481)).
 4.5*   Commercial Bancshares, Inc. Incentive Stock Option Plan for Key Employees.
 4.6*   Form of Stock Option Agreement under the Commercial Bancshares, Inc. Incentive
        Stock Option Plan for Key Employees.
 5.1*   Opinion of Bracewell & Patterson, L.L.P. as to the validity of the Common Stock
        registered hereunder.
23.1*   Consent of Deloitte & Touche LLP.
23.2*   Consent of Bracewell & Patterson, L.L.P. (included in the opinion filed as Exhibit 5.1
        hereto).
24.1*   Powers of Attorney (included on signature page hereto).
</TABLE>
____________________________
*  Filed herewith.

                                      II-2
<PAGE>

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

     (a) The undersigned registrant hereby undertakes:

          (1) To file, during any period in which offers or sales are being made
     of the securities registered hereby, 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 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) 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;

               (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 the undertakings set forth in paragraphs
          (a)(1)(i) and (a)(1)(ii) above do not apply if the information
          required to be included in a post-effective amendment by those
          paragraphs is contained in periodic reports filed by the registrant
          pursuant to Section 13 or Section 15(d) of the Securities Exchange Act
          of 1934 that are incorporated by reference in this registration
          statement.

          (2) That, for the purpose of determining any liability under the
     Securities Act of 1933, each such post-effective amendment should 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 the purposes of
determining any liability under the Securities Act of 1933, each filing of the
registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 that is incorporated by reference in the
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 of 1933 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 Securities and Exchange
Commission such indemnification is against public policy as expressed in the Act
and is, therefore, unenforceable.  In the

                                      II-3
<PAGE>

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 Act and
will be governed by the final adjudication of such issue.

                                      II-4
<PAGE>

                                   SIGNATURES

     PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, AS AMENDED, 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 OR AMENDMENT TO BE SIGNED ON ITS BEHALF BY THE UNDERSIGNED, THEREUNTO
DULY AUTHORIZED, IN THE CITY OF HOUSTON, STATE OF TEXAS ON THE 16TH DAY OF
MARCH, 2001.

                         PROSPERITY BANCSHARES, INC.
                                  (Registrant)


                         By:     /s/ David Zalman
                            ---------------------------------------
                              David Zalman
                              President and Chief Executive Officer

                                      II-5
<PAGE>

                               POWER OF ATTORNEY

     Each person whose signature appears below hereby constitutes and appoints
Ned S. Holmes and David Zalman, with full power to each of them to act without
the other, the undersigned's true and lawful attorney-in-fact and agent, with
full power of substitution and resubstitution, for the undersigned and in the
undersigned's name, place and stead, in any and all capacities (until revoked in
writing), to sign this Registration Statement on Form S-8 and any and all
amendments (including post-effective amendments) thereto, to file the same,
together with all exhibits thereto and documents in connection therewith, with
the Securities and Exchange Commission, to sign any and all applications,
registration statements, notices and other documents necessary or advisable to
comply with the applicable state securities authorities, granting unto said
attorney-in-fact and agent, or his or their substitute or substitutes, 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 in order to effectuate the same
as fully to all intents and purposes as the undersigned might or could do if
personally present, thereby ratifying and confirming all that said attorneys-in-
fact and agents, or his or their substitute or substitutes, may lawfully do or
cause to be done by virtue hereof.

     PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, THIS
REGISTRATION STATEMENT OR AMENDMENT HAS BEEN SIGNED BY THE FOLLOWING PERSONS IN
THE CAPACITIES INDICATED AND ON THE 16TH DAY OF MARCH, 2001.


     Signature                                      Title
     ---------                                      -----

/s/ David Zalman                President and Chief Executive Officer
-------------------------       (principal executive officer)
David Zalman


/s/ David Hollaway              Chief Financial Officer
-------------------------       (principal financial officer and principal
David Hollaway                  accounting officer)


/s/ Harry Bayne                 Director
-------------------------
Harry Bayne


                                Director
-------------------------
James A. Bouligny


/s/ Charles A. Davis, Jr.       Director
-------------------------
Charles A. Davis, Jr.


/s/ J. T. Herin                 Director
-------------------------
J. T. Herin


/s/ Ned S. Holmes               Director
-------------------------
Ned S. Holmes

                                      II-6
<PAGE>

/s/ A. Virgil Pace              Director
-------------------------
A. Virgil Pace

                                Director
-------------------------
Tracy T. Rudolph


/s/ Charles M. Slavik           Director
-------------------------
Charles M. Slavik


/s/ Harrison Stafford II        Director
-------------------------
Harrison Stafford II


/s/ Robert Steelhammer          Director
-------------------------
Robert Steelhammer


/s/ H. E. Timanus, Jr.          Director
-------------------------
H. E. Timanus, Jr.

                                      II-7
<PAGE>

                               INDEX TO EXHIBITS


<TABLE>
<C>     <S>
  4.1   Form of certificate representing shares of Prosperity common stock (incorporated
        herein by reference to Exhibit 4 to the Company's Registration Statement on Form S-1
        (Registration No. 333-63267))
  4.2   Form of Indenture by and between Prosperity Bancshares, Inc. and First Union Trust
        Company, National Association with respect to the Junior Subordinated Debentures of
        Prosperity Bancshares, Inc. (incorporated by reference from Exhibit 4.1 to the
        Company's Registration Statement on Form S-1 (Registration No. 333-89481))
  4.3   Form of Amended and Restated Trust Agreement of Prosperity Capital Trust I
        (incorporated by reference from Exhibit 4.5 to the Company's Registration Statement
        on Form S-1 (Registration No. 333-89481)
  4.4   Form of Trust Preferred Securities Guarantee Agreement by and between Prosperity
        Bancshares, Inc. and First Union Trust Company, National Association (incorporated
        by reference from Exhibit 4.7 to the Company's Registration Statement on Form S-1
        Registration No. 333-89481))
 4.5*   Commercial Bancshares, Inc. Incentive Stock Option Plan for Key Employees.
 4.6*   Form of Stock Option Agreement under the Commercial Bancshares, Inc. Incentive
        Stock Option Plan for Key Employees.
 5.1*   Opinion of Bracewell & Patterson, L.L.P. as to the validity of the Common Stock
        registered hereunder.
23.1*   Consent of Deloitte & Touche LLP.
23.2*   Consent of Bracewell & Patterson, L.L.P. (included in the opinion filed as Exhibit 5.1
        hereto).
24.1*   Powers of Attorney (included on signature page hereto).
</TABLE>
____________________________
*  Filed herewith.
[{"type": "S-8", "sequence": "1", "filename": "0001.txt", "description": "FORM S-8", "secsgml_size_bytes": 21107}]
{"company-data": {"conformed-name": "PROSPERITY BANCSHARES INC", "cik": "0001068851", "assigned-sic": "6022", "irs-number": "742331986", "state-of-incorporation": "TX", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-57238", "film-number": "1571944"}, "business-address": {"street1": "55 WAUGH", "street2": "STE 1111", "city": "HOUSTON", "state": "TX", "zip": "77007", "phone": "7136211880"}, "mail-address": {"street1": "4295 SAN FELIPE", "city": "HOUSTON", "state": "TX", "zip": "77027"}}
As filed with the Securities and Exchange Commission on March 19, 2001

                                                  REGISTRATION NO. 333-_________
================================================================================

                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
                              --------------------
                                    FORM S-8
            REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
                                   __________

                          PROSPERITY BANCSHARES, INC.
             (Exact name of registrant as specified in its charter)

            TEXAS                                            74-2331986
(State or other jurisdiction of                           (I.R.S. Employer
incorporation or organization)                           Identification No.)
                             ---------------------
                                4295 SAN FELIPE
                              HOUSTON, TEXAS 77027
                                 (713) 693-9300
          (Address of Principal Executive Offices Including Zip Code)

                             ---------------------
   COMMERCIAL BANCSHARES, INC. INCENTIVE STOCK OPTION PLAN FOR KEY EMPLOYEES
                             (Full title of Plan)
                             ---------------------
                                  DAVID ZALMAN
                          PROSPERITY BANCSHARES, INC.
                                4295 SAN FELIPE
                              HOUSTON, TEXAS 77027
                    (Name and address of agent for service)

                                 (713) 693-9300
         (Telephone number, including area code, of agent for service)

                                    Copy to:

                              WILLIAM T. LUEDKE IV
                         BRACEWELL & PATTERSON, L.L.P.
                           SOUTH TOWER PENNZOIL PLACE
                        711 LOUISIANA STREET, SUITE 2900
                           HOUSTON, TEXAS 77002-2781
                                 (713) 223-2900
                                  ____________
                        CALCULATION OF REGISTRATION FEE
PROPOSED MAXIMUM          PROPOSED MAXIMUM       AMOUNT OF
 TITLE OF SECURITIES       AMOUNT TO BE          OFFERING PRICE          AGGREGATE OFFERING     REGISTRATION
   TO BE REGISTERED       REGISTERED(1)      PER SHARE(1)(2)(3)(4)       PRICE(1)(2)(3)(4)          FEE
Common Stock,             12,090 shares             $ 1.45(3)                  $56,026             $14.00
$1.00 par value                                     $10.32(4)
----------------------
(1)       This Registration Statement shall also include any additional shares
          of Common Stock which may be offered and  issued pursuant to the
          antidilution provisions of the Plan.
(2)       Estimated solely for purposes of calculating the registration fee in
          accordance with Rule 457(h).
(3)       7,750 shares under the Plan are valued at an exercise price of $1.45
          pursuant to options to acquire such shares which are outstanding under
          the plan.
(4)       4,340 shares under the Plan are valued at an exercise price of $10.32
          pursuant to options to acquire such shares which are outstanding under
          the Plan.
PART I

             INFORMATION REQUIRED IN THE SECTION 10(A) PROSPECTUS

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

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

*         The information required by Items 1 and 2 of Part I of Form S-8 is
          omitted from this Registration Statement in accordance with the Note
          to Part 1 of Form S-8 and Rule 428 promulgated under the Securities
          Act of 1933, as amended (the "Securities Act").
PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

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

     The following documents filed by Prosperity Bancshares, Inc., a Texas
corporation (the "Company"), (Commission File No. 000-25051) with the Securities
and Exchange Commission (the "Commission") are incorporated by reference into
this Registration Statement as of their respective dates:

          1.  The Company's Annual Report on Form 10-K for the year ended
     December 31, 2000;

          2.  The Company's Current Report on Form 8-K under Item 2 dated March
     1, 2001; and

          3.  The description of the common stock, par value $1.00 per share,
     contained in the Company's Registration Statement on Form 8-A, dated
     November 10, 1998.

     All documents filed by the Company pursuant to Sections 13(a), 13(c), 14
and 15(d) of the Securities Exchange Act of 1934, as amended (the "Exchange
Act"), after the date of this Registration Statement and prior to the filing of
a post-effective amendment hereto which indicates that all securities offered
have been sold or which deregisters all such securities then remaining unsold,
shall be deemed to be incorporated herein by reference and to be a part hereof
from the date of filing such documents.  Any statement contained herein or in
any 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 in any other subsequently
filed document which also is or is deemed to be incorporated by reference herein
modifies or supersedes such statement.  Any such statement so modified or
superseded shall not be deemed to constitute a part of this Registration
Statement, except as so modified or superseded.

Item 4.   Description of Securities.
          -------------------------

     Not applicable.

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

     Not applicable.

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

     The Registrant's Amended and Restated Articles of Incorporation (the
"Articles of Incorporation") and Amended and Restated Bylaws ("Bylaws") require
the Registrant to indemnify officers and directors of the Registrant to the
fullest extent permitted by Article 2.02-1 of the Texas Business Corporation Act
("TBCA") of the State of Texas.  Generally, Article 2.02-1 of the TBCA permits a
corporation to indemnify a person who was, is, or is threatened to be a named
defendant or respondent in a proceeding because the person was or is a director
or officer if it is determined that such person (i) conducted himself in good
faith, (ii) reasonably believed (a) in the case of conduct in his official
capacity as a director or officer of the corporation, that his conduct was in
the corporation's best interests or (b) in the case of other situations, that
his conduct was at least not opposed to the corporation's best interests and
(iii) in the case of any criminal proceeding, had no reasonable cause to believe
that his conduct was unlawful.  In addition, the TBCA requires a corporation to
indemnify a director or officer for any action that such director or officer is
wholly successful in defending on the merits.

                                      II-1
The Company's Articles of Incorporation provide that a director of the
Company will not be liable to the corporation for monetary damages for an act or
omission in the director's capacity as a director, except to the extent not
permitted by law.  Texas law does not permit exculpation of liability in the
case of (i) a breach of the director's duty of loyalty to the corporation or its
shareholders, (ii) an act or omission not in good faith that involves
intentional misconduct or a knowing violation of the law, (iii) a transaction
from which a director received an improper benefit, whether or not the benefit
resulted from an action taken within the scope of the director's office or (iv)
an act or omission for which the liability of the director is expressly provided
by statute.

     The Company may provide liability insurance for each director and officer
for certain losses  arising from claims or charges made against them while
acting in their capabilities as directors or officers of the Company, whether or
not the Registrant would have the power to indemnify such person against such
liability, as permitted by law.

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

          Not applicable.

Item 8.   Exhibits.
          ---------
4.1   Form of certificate representing shares of Prosperity common stock (incorporated
        herein by reference to Exhibit 4 to the Company's Registration Statement on Form S-1
        (Registration No. 333-63267)).
  4.2   Form of Indenture by and between Prosperity Bancshares, Inc. and First Union Trust
        Company, National Association with respect to the Junior Subordinated Debentures of
        Prosperity Bancshares, Inc. (incorporated by reference from Exhibit 4.1 to the
        Company's Registration Statement on Form S-1 (Registration No. 333-89481)).
  4.3   Form of Amended and Restated Trust Agreement of Prosperity Capital Trust I
        (incorporated by reference from Exhibit 4.5 to the Company's Registration Statement
        on Form S-1 (Registration No. 333-89481).
  4.4   Form of Trust Preferred Securities Guarantee Agreement by and between Prosperity
        Bancshares, Inc. and First Union Trust Company, National Association (incorporated
        by reference from Exhibit 4.7 to the Company's Registration Statement on Form S-1
        Registration No. 333-89481)).
 4.5*   Commercial Bancshares, Inc. Incentive Stock Option Plan for Key Employees.
 4.6*   Form of Stock Option Agreement under the Commercial Bancshares, Inc. Incentive
        Stock Option Plan for Key Employees.
 5.1*   Opinion of Bracewell & Patterson, L.L.P. as to the validity of the Common Stock
        registered hereunder.
23.1*   Consent of Deloitte & Touche LLP.
23.2*   Consent of Bracewell & Patterson, L.L.P. (included in the opinion filed as Exhibit 5.1
        hereto).
24.1*   Powers of Attorney (included on signature page hereto).
____________________________
*  Filed herewith.

                                      II-2
Item 9.   Undertakings.
          ------------

     (a) The undersigned registrant hereby undertakes:

          (1) To file, during any period in which offers or sales are being made
     of the securities registered hereby, 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 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) 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;

               (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 the undertakings set forth in paragraphs
          (a)(1)(i) and (a)(1)(ii) above do not apply if the information
          required to be included in a post-effective amendment by those
          paragraphs is contained in periodic reports filed by the registrant
          pursuant to Section 13 or Section 15(d) of the Securities Exchange Act
          of 1934 that are incorporated by reference in this registration
          statement.

          (2) That, for the purpose of determining any liability under the
     Securities Act of 1933, each such post-effective amendment should 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 the purposes of
determining any liability under the Securities Act of 1933, each filing of the
registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 that is incorporated by reference in the
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 of 1933 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 Securities and Exchange
Commission such indemnification is against public policy as expressed in the Act
and is, therefore, unenforceable.  In the

                                      II-3
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 Act and
will be governed by the final adjudication of such issue.

                                      II-4
SIGNATURES

     PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, AS AMENDED, 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 OR AMENDMENT TO BE SIGNED ON ITS BEHALF BY THE UNDERSIGNED, THEREUNTO
DULY AUTHORIZED, IN THE CITY OF HOUSTON, STATE OF TEXAS ON THE 16TH DAY OF
MARCH, 2001.

                         PROSPERITY BANCSHARES, INC.
                                  (Registrant)

                         By:     /s/ David Zalman
                            ---------------------------------------
                              David Zalman
                              President and Chief Executive Officer

                                      II-5
POWER OF ATTORNEY

     Each person whose signature appears below hereby constitutes and appoints
Ned S. Holmes and David Zalman, with full power to each of them to act without
the other, the undersigned's true and lawful attorney-in-fact and agent, with
full power of substitution and resubstitution, for the undersigned and in the
undersigned's name, place and stead, in any and all capacities (until revoked in
writing), to sign this Registration Statement on Form S-8 and any and all
amendments (including post-effective amendments) thereto, to file the same,
together with all exhibits thereto and documents in connection therewith, with
the Securities and Exchange Commission, to sign any and all applications,
registration statements, notices and other documents necessary or advisable to
comply with the applicable state securities authorities, granting unto said
attorney-in-fact and agent, or his or their substitute or substitutes, 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 in order to effectuate the same
as fully to all intents and purposes as the undersigned might or could do if
personally present, thereby ratifying and confirming all that said attorneys-in-
fact and agents, or his or their substitute or substitutes, may lawfully do or
cause to be done by virtue hereof.

     PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, THIS
REGISTRATION STATEMENT OR AMENDMENT HAS BEEN SIGNED BY THE FOLLOWING PERSONS IN
THE CAPACITIES INDICATED AND ON THE 16TH DAY OF MARCH, 2001.

     Signature                                      Title
     ---------                                      -----

/s/ David Zalman                President and Chief Executive Officer
-------------------------       (principal executive officer)
David Zalman

/s/ David Hollaway              Chief Financial Officer
-------------------------       (principal financial officer and principal
David Hollaway                  accounting officer)

/s/ Harry Bayne                 Director
-------------------------
Harry Bayne

                                Director
-------------------------
James A. Bouligny

/s/ Charles A. Davis, Jr.       Director
-------------------------
Charles A. Davis, Jr.

/s/ J. T. Herin                 Director
-------------------------
J. T. Herin

/s/ Ned S. Holmes               Director
-------------------------
Ned S. Holmes

                                      II-6
/s/ A. Virgil Pace              Director
-------------------------
A. Virgil Pace

                                Director
-------------------------
Tracy T. Rudolph

/s/ Charles M. Slavik           Director
-------------------------
Charles M. Slavik

/s/ Harrison Stafford II        Director
-------------------------
Harrison Stafford II

/s/ Robert Steelhammer          Director
-------------------------
Robert Steelhammer

/s/ H. E. Timanus, Jr.          Director
-------------------------
H. E. Timanus, Jr.

                                      II-7
INDEX TO EXHIBITS
4.1   Form of certificate representing shares of Prosperity common stock (incorporated
        herein by reference to Exhibit 4 to the Company's Registration Statement on Form S-1
        (Registration No. 333-63267))
  4.2   Form of Indenture by and between Prosperity Bancshares, Inc. and First Union Trust
        Company, National Association with respect to the Junior Subordinated Debentures of
        Prosperity Bancshares, Inc. (incorporated by reference from Exhibit 4.1 to the
        Company's Registration Statement on Form S-1 (Registration No. 333-89481))
  4.3   Form of Amended and Restated Trust Agreement of Prosperity Capital Trust I
        (incorporated by reference from Exhibit 4.5 to the Company's Registration Statement
        on Form S-1 (Registration No. 333-89481)
  4.4   Form of Trust Preferred Securities Guarantee Agreement by and between Prosperity
        Bancshares, Inc. and First Union Trust Company, National Association (incorporated
        by reference from Exhibit 4.7 to the Company's Registration Statement on Form S-1
        Registration No. 333-89481))
 4.5*   Commercial Bancshares, Inc. Incentive Stock Option Plan for Key Employees.
 4.6*   Form of Stock Option Agreement under the Commercial Bancshares, Inc. Incentive
        Stock Option Plan for Key Employees.
 5.1*   Opinion of Bracewell & Patterson, L.L.P. as to the validity of the Common Stock
        registered hereunder.
23.1*   Consent of Deloitte & Touche LLP.
23.2*   Consent of Bracewell & Patterson, L.L.P. (included in the opinion filed as Exhibit 5.1
        hereto).
24.1*   Powers of Attorney (included on signature page hereto).
____________________________
*  Filed herewith.