<PAGE>
                                                                     EXHIBIT 4.5
 
                     AMENDED AND RESTATED VOTING AGREEMENT


          THIS AMENDED AND RESTATED VOTING AGREEMENT (the "Agreement") is
entered into as of January 22, 1997, by and among the stockholders named on the
signature pages hereto (each a "Stockholder" and, collectively, the
"Stockholders") and Sterling Chemicals Holdings, Inc. (the "Company").

          WHEREAS, the Stockholders are beneficial owners of common stock, par
value $.01 per share, of the Company ("Common Stock");

          WHEREAS, the Stockholders and the Company (formerly named Sterling
Chemicals, Inc. and successor-in-interest to STX Acquisition Corp.) heretofore
entered into a Voting Agreement dated as of August 12, 1996 (the "Original
Voting Agreement"); and

          WHEREAS, the parties hereto desire to amend the Original Voting
Agreement in certain respects and to restate the Original Voting Agreement, as
so amended, in its entirety.

          NOW, THEREFORE, the parties hereto, in consideration of the mutual
covenants and agreements herein contained, and intending to be legally bound
hereby, covenant and agree as follows:

                                   ARTICLE I
                         Definitions and Interpretation

          1.1. Definitions.  As used in this Agreement, the following terms
shall have the meanings provided below:

          "Annual Clipper Designation" has the meaning specified in Section 3.2.

          "Annual Koch Designation" has the meaning specified in Section 4.2.

          "Annual Meeting" means an annual meeting of the stockholders of the
          Company.

          "Board" means the board of directors of the Company.

          "Clipper Designee" means a person designated as a nominee for election
     to the Board pursuant to Article III.

          "Clipper Director" means a director of the Company designated by the
     Clipper Representative pursuant to Article III.
<PAGE>
 
          "Clipper Investors" means (i) Clipper Capital Associates, L.P., (ii)
     Clipper Equity Partners I, L.P., (iii) Clipper/Merchant Partners, L.P.,
     (iv) Clipper/European Re, L.P., Clipper/Merban, L.P., (v) CS First Boston
     Merchant Investments 1995/96, L.P., (vi) certain accredited investors who
     enter into agreements with Clipper Capital Associates, L.P. under which
     such partnership acts as a nominee with respect to Common Stock purchased
     on behalf of such investors and who are identified as Clipper Investors by
     written notice given by Clipper Capital Associates, L.P. to the Company and
     (vii) those employees of CS First Boston Corporation who enter into
     subscription agreements with the Company and who are indentified as Clipper
     Investors by written notice given by Clipper Capital Associates, L.P. to
     the Company.

           "Clipper Observer" has the meaning specified in Section 3.6.

           "Clipper Representative" means Clipper Equity Partners I, L.P. so
     long as it holds Common Stock and thereafter means all the remaining
     Clipper Investors.

          "Koch" means Koch Capital Services, Inc.

          "Koch Designee" means a person designated for election to the Board
     pursuant to Article IV.

          "Koch Director" means a director of the Company designated by Koch
     pursuant to Article IV.

          "Voting Stock" means Common Stock and any other class of capital stock
     of the Company entitled to vote generally in an election of directors.

          1.2.  Interpretation.  (a)  In this Agreement, unless a contrary
intention appears:

          (i) the singular number includes the plural number and vice versa;

          (ii) reference to any gender includes each other gender;

          (iii)  the words "herein," hereof" and "hereunder" and other words of
     similar import refer to this Agreement as a whole and not to any particular
     Article, Section or other subdivision;

          (iv) reference to any person or entity includes such person's or
     entity's successors and assigns but, if applicable, only if such successors
     and assigns are permitted by this Agreement, and reference to a person or
     entity in a particular capacity excludes such person or entity in any other
     capacity or individually;

                                      -2-
<PAGE>
 
          (v) reference to any agreement, document or instrument means such
     agreement, document or instrument as amended, supplemented or modified and
     in effect from time to time in accordance with the terms thereof; and

          (vi) reference to any Article or Section means such Article or Section
     hereof.

          (b) The Article and Section headings herein are for convenience only
and shall not affect the construction hereof.

          (c) This Agreement shall be deemed drafted jointly by all the parties
hereto and shall not be specifically construed against any party hereto based on
any claim that such party or its legal counsel drafted such provision.

                                   ARTICLE II
                                 Size of Board

          The parties hereto acknowledge and agree that, so long as the Clipper
Representative shall be entitled to designate a director nominee in accordance
with Article III or Koch shall be entitled to designate a director nominee in
accordance with Article IV, the Board shall at all times consist of at least
seven directors.

                                  ARTICLE III
                       The Clipper Director and Observer

          3.1. General.  The Clipper Representative shall be entitled to
designate one individual as a director nominee to serve on the Board. Such
designation shall be made annually as provided in Section 3.2 or at other times
as provided in Section 3.3. The parties hereto acknowledge that Robert B.
Calhoun has heretofore been designated and elected as the initial Clipper
Director. The Clipper Director shall serve on the Board until a successor
director shall be duly elected and qualified or until his earlier death, removal
or resignation.

          3.2. Annual Clipper Designations.  The Company shall, no later than 45
days prior to the mailing of any proxy statement with respect to an Annual
Meeting, notify the Clipper Representative of the date of such mailing.  As soon
as practicable after receipt of such notice but in any event no later than 20
days prior to the mailing date specified therein, the Clipper Representative
shall provide the Company a written instrument ("Annual Clipper Designation")
designating either the incumbent Clipper Director or a person other than the
incumbent Clipper Director, in which event the Annual Clipper Designation shall
include such other person's name, age, principal occupation, business address
and telephone number and residence address and telephone number.  The Annual
Clipper Designation shall also include or be accompanied by (i) all information
relating to the person designated therein that is required to be disclosed in
the proxy statement pursuant to applicable regulations of the Securities and
Exchange Commission, (ii) such person's consent to being named in the proxy
statement as a nominee and (iii) a statement of such person's intention to serve
as a director if elected to the Board. The Company shall nominate for

                                      -3-
<PAGE>
 
election at such Annual Meeting the person designated in the Annual Clipper
Designation. Subject to applicable laws, the Company shall take all other
actions reasonably necessary to cause the Clipper Designee to be elected to the
Board. Each Stockholder agrees to vote (or caused to be voted) the Voting Stock
owned by it in favor of the Clipper Designee and to take any other necessary or
desirable action in its capacity as a stockholder of the Company to cause the
Clipper Designee to be elected to the Board.

          3.3. Interim Clipper Designations.  In case a vacancy shall occur on
the Board because of the death, resignation or removal of the Clipper Director,
the Clipper Representative may elect either (i) to have such vacancy filled at
the next Annual Meeting pursuant to a designation made in accordance with
Section 3.2 or (ii) to have such vacancy filled prior to such Annual Meeting by
a majority of the directors remaining in office.  If the Clipper Representative
wishes to make the election provided for in clause (ii) above, it shall
designate a successor director nominee by written notice given to the Company
and each of the other Stockholders (the "Interim Clipper Designation"). Subject
to applicable laws, the Company shall recommend that the remaining directors
elect the Clipper Designee and shall take all other actions reasonably necessary
to cause the Clipper Designee to be elected to the Board. Each Stockholder
agrees to vote (or cause to be voted) the Voting Stock owned by it in favor of
the Clipper Designee and to take any other necessary or desirable action in its
capacity as a stockholder of the Company to cause the Clipper Designee to be
elected to the Board.  Without limitation of the foregoing, Koch agrees to cause
the Koch Director to vote in favor of the Clipper Designee and each Stockholder
who is a member of the Board agrees, subject to his fiduciary duties, to vote in
favor of the Clipper Designee.

          (b) In the event Clipper shall make an Interim Clipper Designation in
accordance with paragraph (a) above in order to fill the vacancy created by the
death, resignation or removal of the Clipper Director and in the event a
majority of the directors remaining in office shall fail or refuse to appoint
the Clipper Designee to fill such vacancy within 30 days after receipt by the
Company of such Interim Clipper Designation, then the Company agrees, if
requested by Clipper to do so, to call a special meeting of the stockholders of
the Company for the purpose of voting upon a proposal to elect the Clipper
Designee to the Board; provided, however, that in no event shall the Company be
required to call a special meeting of the stockholders if the Company has given
a formal notice of the next Annual Meeting.

          3.4. Failure of Clipper to Designate.  If the Clipper Representative
shall fail or refuse to designate a nominee for director pursuant to Section 3.2
or 3.3, such directorship shall remain vacant unless and until such designation
shall be made as provided in this Article III; provided, however, that if such
vacancy results in less than the minimum number of directors required by law or
by the charter or bylaws of the Company as then in effect, such vacancy shall be
filled by an individual elected by a majority of the directors then serving.

          3.5. Removal of Clipper Director.  The Clipper Representative shall
have the exclusive right (except as otherwise provided by applicable law or the
Company's charter) to remove or replace the Clipper Director.  If the Clipper
Representative desires to remove the Clipper Director, it shall give written
notice of such desire to the Company and the other Stockholders who shall

                                      -4-
<PAGE>
 
thereupon become obligated to vote all Voting Stock owned by them in favor of
the removal of the Clipper Director.  No Stockholder (other than the Clipper
Investors) shall vote any of the securities of the Company owned by it or take
any other action in its capacity as a stockholder of the Company for the removal
of the Clipper Director without the prior written approval of the Clipper
Representative.

          3.6. The Clipper Observer.  The Clipper Representative shall have the
right, exercisable by written notice to the Company, to designate from time to
time an observer (the "Clipper Observer") who shall have the right to attend
meetings of the Board and to receive information delivered to the Board, at the
expense of the Clipper Investors.  The initial Clipper Observer shall be Kevin
A. Macdonald.

          3.7. Termination/Suspension of Clipper Rights.  Notwithstanding
anything in this Agreement to the contrary, the rights of the Clipper Investors
and the Clipper Representative under this Article III and the obligations of the
other parties hereto under this Article III shall terminate immediately and
without notice upon the earlier of (i) the termination of this Agreement under
Section 7.3 and (ii) any event or occurrence resulting in the holding by the
Clipper Investors of less than 5% of the outstanding shares of Common Stock.
Promptly upon the termination of its rights under this Article III, the Clipper
Investors agree to (i) cause the resignation of, or provide notice to the other
parties hereto as provided in Section 3.5 requesting the removal of, the
incumbent Clipper Director and (ii) inform the Clipper Observer that his rights
under Section 3.6 have terminated.

          3.8. Irrevocable Proxy.  Each of the Stockholders hereby grants to the
Clipper Representative, on behalf of  the Clipper Investors, an irrevocable
proxy to vote all shares of Common Stock presently or at any future time owned
beneficially or of record by such Stockholder which the Stockholder is entitled
to vote, and to represent and otherwise act as such Stockholder could act, in
the same manner and with the same effect as if such Stockholder were personally
present, at any annual, special or other meeting of the stockholders of the
Company, and at any adjournment thereof, or pursuant to any written consent in
lieu of meeting or otherwise; provided, however, that any such vote or consent
in lieu thereof or any other action so taken shall be solely for the purposes of
electing a Clipper Designee to the Board as provided in Section 3.2 or 3.3 or
removing the Clipper Director from the Board as provided in Section 3.5.

                                   ARTICLE IV
                               The Koch Director

          4.1. General.  Koch shall be entitled to designate one individual as a
director nominee to serve on the Board. Such designation shall be made annually
as provided in Section 4.2 or at other times as provided in Section 4.3. The
parties hereto acknowledge that George B. Gregory has heretofore been designated
and elected as the initial Koch Director.  The Koch Director shall serve on the
Board until a successor director shall be duly elected and qualified or until
his earlier death, removal or resignation.

                                      -5-
<PAGE>
 
          4.2. Annual Koch Designations.  The Company shall, no later than 45
days prior to the mailing of any proxy statement with respect to an Annual
Meeting, notify Koch of the date of such mailing.  As soon as practicable after
receipt of such notice but in any event no later than 20 days prior to the
mailing date specified therein, Koch shall provide the Company a written
statement ("Annual Koch Designation") designating either the incumbent Koch
Director or a person other than the incumbent Koch Director, in which event the
Annual Koch Designation shall include such other person's name, age, principal
occupation, business address and telephone number and residence address and
telephone number.  The Annual Koch Designation shall also include or be
accompanied by (i) all information relating to the person designated therein
that is required to be disclosed in the proxy statement pursuant to applicable
regulations of the Securities and Exchange Commission, (ii) such person's
consent to being named in the proxy statement as a nominee and (iii) a statement
of such person's intention to serve as a director if elected to the Board. The
Company shall nominate for election at such Annual Meeting the person designated
in the Annual Koch Designation. Subject to applicable laws, the Company agrees
to take all other actions reasonably necessary to cause the Koch Designee to be
elected to the Board. Each Stockholder agrees to vote (or cause to be voted) the
Voting Stock owned by it in favor of the Koch Designee and to take any other
necessary or desirable action in its capacity as a stockholder of the Company to
elect the Koch Designee to the Board.

          4.3. Interim Koch Designations.  (a)  In case a vacancy shall occur on
the Board because of the death, resignation or removal of the Koch Director,
Koch may elect either (i) to have such vacancy filled at the next Annual Meeting
pursuant to a designation made in accordance with Section 4.2 or (ii) to have
such vacancy filled prior to such Annual Meeting by a majority of the directors
remaining in office.  If Koch wishes to make the election provided for in clause
(ii) above, it shall designate a successor director nominee by written notice
given to the Company and each of the other Stockholders (the "Interim Koch
Designation").  Subject to applicable laws, the Company shall recommend that the
remaining directors elect the Koch Designee and shall take all other actions
reasonably necessary to cause the Koch Designee to be elected to the Board.
Each Stockholder agrees to vote the Voting Stock owned by it in favor of the
Koch Designee and to take any other necessary or desirable action in its
capacity as a stockholder of the Company to cause the Koch Designee to be
elected to the Board.  Without limitation of the foregoing, the Clipper
Investors agrees to cause the Clipper Director to vote in favor of the Koch
Designee and each Stockholder who is a member of the Board agrees, subject to
his fiduciary duties, to vote in favor of the Koch Designee.

          (b) In the event Koch shall make an Interim Koch Designation in
accordance with paragraph (a) above in order to fill the vacancy created by the
death, resignation or removal of the Koch Director and in the event a majority
of the directors remaining in office shall fail or refuse to appoint the Koch
Designee to fill such vacancy within 30 days after receipt by the Company of
such Interim Koch Designation, then the Company agrees, if requested by Koch to
do so, to call a special meeting of the stockholders of the Company for the
purpose of voting upon a proposal to elect the Koch Designee to the Board;
provided, however, that in no event shall the Company be required to call a
special meeting of the stockholders if the the Company has given a formal notice
of the next Annual Meeting.

                                      -6-
<PAGE>
 
          4.4. Failure of Koch to Designate.  If Koch shall fail or refuse to
designate a nominee for director pursuant to Section 4.2 or 4.3, such
directorship shall remain vacant unless and until such designation shall be made
as provided in this Article IV; provided, however, that if such vacancy results
in less than the minimum number of directors required by law or by the charter
or bylaws of the Company as then in effect, such vacancy shall be filled by an
individual elected by a majority of the directors then serving.

          4.5. Removal of Koch Director.  Koch shall have the exclusive right
(except as otherwise provided by applicable law) to remove or replace the Koch
Director.  If Koch desires to remove the Koch Director, it shall give written
notice of such desire to the Company and the other Stockholders who shall
thereupon become obligated to vote all Voting Stock owned by them in favor of
the removal of the Koch Director.  No Stockholder (other than  Koch) shall vote
any of the securities of the Company owned by it or take any other action in its
capacity as a stockholder of the Company for the removal of the Koch Director
without the prior written approval of Koch.

          4.6. Termination/Suspension of Koch Rights.  Notwithstanding anything
in this Agreement to the contrary, the rights of Koch under this Article IV and
the obligations of the other parties hereto under this Article IV shall
terminate immediately and without notice upon the earlier of (i) the termination
of this Agreement under Section 7.3 and (ii) any event or occurrence resulting
in the holding by Koch of less than 5% of the outstanding shares of Common
Stock.  Promptly upon the termination of its rights under this Article IV, Koch
agrees to cause the resignation of, or provide notice to the other parties
hereto as provided in Section 4.5 requesting the removal of, the incumbent Koch
Director.

          4.7. Irrevocable Proxy.  Each of the Stockholders hereby grants to
Koch an irrevocable proxy to vote all shares of Common Stock presently or at any
future time owned beneficially or of record by such Stockholder which the
Stockholder is entitled to vote, and to represent and otherwise act as such
Stockholder could act, in the same manner and with the same effect as if such
Stockholder were personally present, at any annual, special or other meeting of
the stockholders of the Company, and at any adjournment thereof, or pursuant to
any written consent in lieu of meeting or otherwise; provided, however, that any
such vote or consent in lieu thereof or any other action so taken shall be
solely for the purposes of electing a Koch Designee to the Board as provided in
Section 4.2 or 4.3 or removing the Koch Director from the Board as provided in
Section 4.5.



                                   ARTICLE V
               Certain Restrictions on Sale of Common Stock, etc.

          5.1.  Stock Legend.  (a)  Each certificate for shares of Common Stock
owned by any Stockholder shall bear the following legend:

                                      -7-
<PAGE>
 
          The shares represented by this certificate are subject to the terms
          and conditions of a Voting Agreement, a copy of which is on file with
          the Secretary of Sterling Chemicals Holdings, Inc., and are held and
          may be sold, assigned, transferred or otherwise disposed of only in
          accordance with such agreement.

          (b) Upon the termination of this Agreement under Section 7.3, the
Company shall, without charge and upon surrender of certificates by the holders
thereof and written request of such holders, cancel all certificates evidencing
shares of Common Stock bearing the legend described above and issue to the
holders thereof replacement certificates that do not bear such legend for an
equal number of shares held by such holders.  Upon the transfer of any Common
Stock bearing the legend described above to a party believed by the Company to
be not bound by and subject to this Agreement by virtue of Section 7.2, the
Company shall, without charge and upon surrender of certificates by the holders
thereof and written request of either the transferor or transferee, cancel all
certificates evidencing such shares of Common Stock and issue to the transferee
thereof replacement certificates that do not bear such legend.

          5.2. Voting Trusts, etc.  No Stockholder shall deposit any shares of
Common Stock in a voting trust or subject any shares of Common Stock to any
arrangement or agreement (other than this Agreement) with respect to the voting
of such shares unless such trust or arrangement or agreement is made expressly
subject to the provisions of this Agreement.  Except as provided in this
Agreement, no Stockholder shall give any proxy or power of attorney with respect
to any shares of Common Stock that permits the holder thereof to vote such
shares in its discretion in an election of directors or for the removal of the
Clipper Director or the Koch Director unless such proxy or power of attorney is
made expressly subject to the provisions of this Agreement.

                                   ARTICLE VI
                         Representations and Warranties

          Each party hereto hereby represents and warrants, severally and not
jointly, to each other party hereto as follows:

          (a) Such party has all necessary power and authority to execute and
     deliver this Agreement and to consummate the transactions contemplated
     hereby.

          (b) Assuming this Agreement has been duly and validly authorized,
     executed and delivered by the other parties hereto, this Agreement
     constitutes a valid and binding agreement of such party, enforceable in
     accordance with its terms.

          (c)  Neither the execution and delivery of this Agreement by such
     party nor the consummation by such party of the transactions contemplated
     hereby will conflict with or constitute a violation of or default under any
     contract, commitment, agreement, arrangement or restriction of any kind to
     which such party is a party or by which such party is bound.

                                      -8-
<PAGE>
 
                                  ARTICLE VII
                            Miscellaneous Provisions

          7.1.      Specific Performance.  The parties hereto agree that
irreparable damage would occur in the event that any of the provisions of this
Agreement were not performed in accordance with their specific terms or were
otherwise breached.  It is accordingly agreed that the parties hereto shall be
entitled to an injunction or injunctions to prevent breaches of the provisions
of this Agreement and to enforce specifically the terms and provisions hereof in
any court of the United States or any state thereof having jurisdiction (this
being in addition to any other remedy to which they are entitled at law or in
equity), and each party hereto agrees to waive in any action for such
enforcement the defense that a remedy at law would be adequate.

          7.2.  Agreement Binding on Certain Transferees. Prior to any transfer
of shares of Common Stock by any Stockholder (excluding any transfer pursuant to
(i) a bona fide public offering of such shares or (ii) a sale of such shares
pursuant to Rule 144 under the Securities Act of 1933, as amended), the
transferee of such shares must agree in writing to become bound by the terms of
this Agreement.  For purposes of this Agreement, all references to Stockholders
shall be deemed to refer to the Stockholders and all direct and indirect
transferees thereof so required to become bound.

          7.3. Term of Agreement.  This Agreement shall terminate on August 21,
2006 or such earlier date as all the parties hereto shall agree upon in writing.
Upon the termination of this Agreement, the rights and obligations hereunder of
the parties hereto shall terminate and the provisions of this Agreement shall be
of no force and effect.  In no event shall this Agreement become effective until
executed and delivered (in one or more counterparts) by all the parties hereto.

          7.4. Reliance on Opinions of Counsel.    (a) The Company shall not be
obligated to take any action hereunder which is contrary to applicable law.  The
Company may rely and shall be fully protected in acting upon any notice,
request, consent, approval or other paper or document reasonably believed by it
to be genuine and to have been signed or presented by the proper person or
persons.  The Company may consult with, and obtain advice from, legal counsel in
the event any question as to any of  its duties hereunder and it shall incur no
liability and shall be fully protected in acting or refusing to act in good
faith in accordance with the written opinion or advice of such counsel.

          (b) Any notice, request, designation, consent or approval given or
made by any Stockholder hereunder shall be conclusive and binding on the
successors, assigns and transferees of such Stockholder.

          (c) For the purpose of determining the number of shares of Voting
Stock owned or held by any Stockholder, the Company may rely and shall be fully
protected in acting upon the stock records maintained by or on behalf of the
Company.

          7.5.  No Inconsistent Actions.  No party hereto shall, directly or
indirectly, undertake any course of action inconsistent with the provisions or
intent of this Agreement.  Without limitation

                                      -9-
<PAGE>
 
of the foregoing, each party hereto agrees that it will not amend or cause to be
amended the provisions of the Company's charter or bylaws if such amendment
would create a conflict or inconsistency between this Agreement and the
Company's charter or bylaws.

          7.6.   Assignment.  This Agreement shall be binding upon and inure to
the benefit of the parties hereto and their respective successors and permitted
assigns.

          7.7. Amendments.  Except as otherwise specifically provided herein,
this Agreement shall not be amended other than by an instrument in writing
signed by all of the parties hereto.

          7.8. Notices.  Any notice, request or communication shall be
sufficiently given if given in writing addressed as indicated on the signature
pages hereof. Notice shall be deemed given when transmitted by telex or
telecopier, delivered to the telegraph or cable office or personally delivered
or, in the case of a mailed notice, three business days after the date deposited
in the United States mails.  Each party hereto, by written notice to the other
parties, may designate additional or different addresses for subsequent notices
or communications.

          7.9. Counterparts.  This Agreement may be executed in counterparts,
each of which when executed shall be deemed an original, but all of which
together shall constitute one and the same agreement.

          7.10.     Entire Agreement.  This Agreement contains the entire
agreement among the parties hereto with respect to the subject matter hereof and
supersedes all prior arrangements or understandings with respect to the subject
matter hereof.

          7.11.     Conflict with Governing Documents.   In the event of a
conflict between this Agreement and the certificate of incorporation or the
bylaws of the Company, the provisions of this Agreement shall govern.

          7.12.     Governing Law.  THE LAWS OF THE JURISDICTION IN WHICH
HOLDINGS IS INCORPORATED, THE STATE OF DELAWARE, SHALL GOVERN THIS AGREEMENT
WITHOUT REGARD TO PRINCIPLES OF CONFLICTS OF LAW.

                                      -10-
<PAGE>
 
          IN WITNESS WHEREOF, the parties hereto have caused this Agreement to
be duly executed under their respective seals, as of the day and year first
written above.
 
                            THE COMPANY:
 
                            STERLING CHEMICALS HOLDINGS, INC.
                            1200 Smith Street, Suite 1900
                            Houston, Texas 77002
                            Attention:   General Counsel and Secretary
                            FAX: 713-654-9577


                            By:   /s/ FRANK P. DIASSI
                               -------------------------------------------
                                    Frank P. Diassi, Chairman of the Board


                            STOCKHOLDERS:

                            FRANK P. DIASSI AND MARIANNE R. DIASSI
                            JOINT TENANTS WITH RIGHT OF SURVIVORSHIP
                            6 Commerce Drive
                            Cranford, New Jersey
                            FAX:
                                 -----------------------------------------

                                  /s/ FRANK P. DIASSI
                                 -----------------------------------------
                                 Frank P. Diassi


                                  /s/ MARIANNE R. DIASSI
                                 -----------------------------------------
                                 Marianne R. Diassi

 

                                      -11-
<PAGE>
 
                            WILLIAM C. AND MARGARET W. OEHMIG
                            TENANTS IN COMMON
                            8 Greenway Plaza, Suite 702
                            Houston, Texas 77046
                            FAX:
                                 -----------------------------------------

                                     /s/ WILLIAM C. OEHMIG
                                 -----------------------------------------
                                 William C. Oehmig


                                     /s/ MARGARET W. OEHMIG
                                 ------------------------------------------
                                 Margaret W. Oehmig
 

                            THE RHENEY LIVING TRUST U/A 8/23/93
                            8 Greenway Plaza, Suite 702
                            Houston, Texas 77046
                            FAX:     (713) 877-1824


                               By:   /s/ SUSAN O. RHENEY
                                  ----------------------------------------
                               Name:    Susan O. Rheney, as Trustee
 


                                   /s/ FRANK J. HEVRDEJS
                                ------------------------------------------
                            Name:    Frank J. Hevrdejs
                            Address: 8 Greenway Plaza, Suite 702
                                     Houston, Texas  77046
                            FAX:     (713) 877-1824


                                   /s/ HUNTER NELSON
                                ------------------------------------------
                            Name:    Hunter Nelson
                            Address: 8 Greenway Plaza, Suite 702
                                     Houston, Texas  77046
                            FAX:       (713) 877-1824

                                      -12-
<PAGE>
 
                            CLIPPER CAPITAL ASSOCIATES, L.P., in its
                            individual capacity and as nominee
                            By:  Clipper Capital Associates, Inc.
                                 its general partner


                               By:   /s/ DANIEL V. CAHILLANE
                                  --------------------------------------------
                               Name:     Daniel V. Cahillane
                               Title:    Treasurer & Secretary
                               Address:  11 Madison Avenue
                                         New York, New York  10010
                               FAX:      (212) 448-5442


                            CLIPPER EQUITY PARTNERS I, L.P.
                            By:  Clipper Capital Associates, L.P.
                                 its general partner
                                By:  Clipper Capital Associates, Inc.
                                     its general partner
 

                               By:   /s/ DANIEL V. CAHILLANE
                                  -------------------------------------------
                               Name:     Daniel V. Cahillane
                               Title:    Treasurer & Secretary
                               Address:  11 Madison Avenue
                                         New York, New York  10010
                               FAX:      (212) 448-5442
 

                            CLIPPER/MERCHANT PARTNERS, L.P.
                            By:  Clipper Capital Associates, L.P.
                                its general partner
                                By:  Clipper Capital Associates, Inc.
                                     its general partner


                               By:   /s/ DANIEL V. CAHILLANE
                                  -------------------------------------------
                               Name:     Daniel V. Cahillane
                               Title:    Treasurer & Secretary
                               Address:  11 Madison Avenue
                                         New York, New York  10010
                               FAX:      (212) 448-5442
 

                                      -13-
<PAGE>
 
                            CLIPPER/MERBAN, L.P.
                            By: Clipper Capital Associates, L.P.
                                its general partner
                                By:  Clipper Capital Associates, Inc.
                                     its general partner


                                By:   /s/ DANIEL V. CAHILLANE
                                    --------------------------
                                Name:    Daniel V. Cahillane
                                Title:   Treasurer & Secretary
                                Address: 11 Madison Avenue
                                         New York, New York  10010
                                FAX:     (212) 448-5442


                            CLIPPER/EUROPEAN RE, L.P.
                            By: Clipper Capital Associates, L.P.
                                its general partner
                                By:  Clipper Capital Associates, Inc.
                                     its general partner


                                    By:   /s/ DANIEL V. CAHILLANE
                                        --------------------------
                                    Name:    Daniel V. Cahillane
                                    Title:   Treasurer & Secretary
                                    Address: 11 Madison Avenue
                                             New York, New York  10010
                                    FAX:     (212) 448-5442

                                      -14-
<PAGE>
 
                            CS FIRST BOSTON MERCHANT
                            INVESTMENTS 1995/96, L.P.
                            By:  Merchant Capital, Inc.
                                 its general partner
                                 By:  Clipper Capital Associates, L.P.
                                      Attorney-in-Fact
                                      By:  Clipper Capital Corporation
                                           its general partner


                                    By:   /s/ DANIEL V. CAHILLANE
                                       --------------------------------------
                                    Name:    Daniel V. Cahillane
                                    Title:   Treasurer & Secretary
                                    Address: 11 Madison Avenue
                                             New York, New York  10010
                                    FAX:     (212) 448-5442


                            FSI NO. 2 CORPORATION


                            By: /s/ RAYE G. WHITE
                                ---------------------------------------------
                            Name:     Raye G. White
                            Title:    Executive Vice President
                            Address:  Two Houston Center, Suite 2907
                                      Houston, Texas  77010
                            FAX:      (713) 654-4015


                            KOCH CAPITAL SERVICES, INC.

 
                            By: /s/ PAUL W. BROOKS
                                ----------------------------------------------
                            Name:     Paul W. Brooks
                            Title:    President
                            Address:  4111 East 37th Street North
                                      Wichita, Kansas  67220
                            FAX:      (316) 828-7868

                                      -15-
<PAGE>
 
                            OLYMPUS GROWTH FUND II, L.P.
                            By: OGP II, L.P., its general partner
                                By:  LJM Corporation, a general partner


                                   By:   /s/ LOUIS J. MISCHIANTI
                                       ---------------------------------------
                                   Name:     Louis J. Mischianti
                                   Title:    President
                                   Address:  Metro Center, One Station Place
                                             Stamford, Connecticut  06902
                                   FAX:      (203) 353-5910


                            OLYMPUS EXECUTIVE FUND, L.P.
                            By: OEF, L.P.
                                By: LJM L.L.C., a general partner


                                    By:   /s/ LOUIS J. MISCHIANTI
                                        --------------------------------------
                                    Name:     Louis J. Mischianti
                                    Title:    Member
                                    Address:  Metro Center, One Station Place
                                              Stamford, Connecticut  06902
                                    FAX:      (203) 353-5910

                                      -16-