<PAGE>   1

      As filed with the Securities and Exchange Commission on July 23, 1999

                                                  Registration No. 333-_________



                       SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549

                               ------------------
                                    FORM S-8

                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                                CIENA CORPORATION
             ------------------------------------------------------
             (Exact name of registrant as specified in its charter)

              DELAWARE                                  23-2725311
------------------------------------      --------------------------------------
    (State or other jurisdiction           (I.R.S. employer identification no.)
  of incorporation or organization)




                               1201 WINTERSON ROAD
                               LINTHICUM, MD 21090
                    ----------------------------------------
                    (Address of principal executive offices)

                   OMNIA COMMUNICATIONS, INC. 1997 STOCK PLAN,
                                   AS AMENDED
                   -------------------------------------------
                            (Full title of the plan)

                               MICHAEL O. MCCARTHY
                    VICE PRESIDENT, ASSISTANT GENERAL COUNSEL
                                  AND SECRETARY
                                CIENA CORPORATION
                               1201 WINTERSON ROAD
                               LINTHICUM, MD 21090
                                 (410) 865-8500
-------------------------------------------------------------------------------
(Name, address and telephone number, including area code, of agent for service)

                                    Copy to:
                               AMY BOWERMAN FREED
                             HOGAN & HARTSON L.L.P.
                            111 SOUTH CALVERT STREET
                               BALTIMORE, MD 21202
                                 (410) 659-2700


                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
=============================================================================================================
                                                Proposed              Proposed
  Title of securities      Amount to be      maximum offering     maximum aggregate          Amount of
   to be registered         registered      price per share (1)   offering price (1)    registration fee (1)
-------------------------------------------------------------------------------------------------------------
<S>                        <C>                <C>                    <C>                  <C>
COMMON STOCK, PAR            755,356             $13.87              $ 10,476,788            $ 2,913
VALUE $.01
=============================================================================================================
</TABLE>


(1) The proposed maximum offering price per share is the weighted average
    exercise price of outstanding options. The filing fee is computed under Rule
    457(h)(1) based on the aggregate price at which the options may be
    exercised.
<PAGE>   2

                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

        The documents containing the information specified in Part I will be
separately sent or given to employees participating in the Omnia Communications,
Inc. 1997 Stock Plan, As Amended (the "Stock Plan"), as specified by Rule
428(b)(1) of the Securities Act of 1933, as amended (the "Securities Act"). In
accordance with the instructions to Part I of Form S-8, such documents will not
be filed with the Securities and Exchange Commission (the "Commission") either
as part of this Registration Statement or as prospectuses or prospectus
supplements pursuant to Rule 424 of the Securities Act.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.           INCORPORATION OF DOCUMENTS BY REFERENCE.

        The Company hereby incorporates by reference into this Registration
Statement the following documents filed by it with the Commission:

        (a)     The Company's annual report on Form 10-K for the fiscal year
                ended October 31, 1998, filed on December 10, 1998, and amended
                on April 5, 1999;

        (b)     The Company's reports on Form 10-Q filed on February 18, 1999
                and May 21, 1999, the Company's report on Form 8-K filed on
                April 1, 1999, and amended on April 5, 1999, the Company's
                report on Form 8-K filed on April 5, 1999 and the Company's
                report on Form 8-K filed on July 21, 1999.

        (c)     The description of the Company's common stock contained in the
                Company's Registration Statement on Form 8-A, filed with the
                Commission on January 13, 1997;

        In addition, all documents and reports filed by the Company subsequent
to the date hereof pursuant to Sections 13(a), 13(c), 14, or 15(d) of the
Securities Exchange Act, as amended (the "Exchange Act"), prior to the filing of
a post-effective amendment which indicates that all securities offered have been
sold or which deregisters all securities remaining unsold, shall be deemed to be
incorporated by reference in this Registration Statement and to be a part hereof
from the date of filing of such documents. Any statement contained 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 subsequent 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, except as so modified or superseded, to
constitute a part of this Registration Statement.

ITEM 4. DESCRIPTION OF SECURITIES.

        Not applicable (the Common Stock is registered under Section 12(g) of
the Exchange Act)


<PAGE>   3

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

        Not applicable.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

        Item 14 of Part II of the Registration Statement of the Registrant on
Form S-1 (Registration No. 333-17729) is hereby incorporated by reference into
this Registration Statement.

                                      * * *

        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 Commission, such
indemnification is against public policy as expressed in the Securities Act and
therefore is unenforceable. In the event that a claim for indemnification
against such liabilities is asserted by such person in connection with the
offering of the Common Stock (other than for 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) 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 of whether such indemnification by it is against public policy as
expressed in the Securities Act and will be governed by the final adjudication
of the issue.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

        Not applicable.

ITEM 8. EXHIBITS.

Exhibit
Number                           Description
------                           -----------

4.1     Form of Common Stock Certificate (filed as Exhibit 4.1 to the Initial
        Form S-1 and incorporated herein by reference).


                                     - 2 -
<PAGE>   4

4.2     Rights Agreement dated December 29, 1997 (filed as Exhibit 4.2 to the
        Registrant's Form 8-K dated December 29, 1997 and incorporated herein by
        reference).

4.3     Amendment to Rights Agreement (filed as Exhibit 4.3 to the Registrant's
        Form 8-K dated October 14, 1998 and incorporated herein by reference).

5.1     Opinion of Hogan & Hartson L.L.P. regarding the legality of the
        securities being registered.

23.1    Consent of PricewaterhouseCoopers LLP.

23.2    Consent of Hogan & Hartson L.L.P. (included in their opinion filed as
        Exhibit 5.1 hereto).

24.1    Power of Attorney (included on signature page).



                                     - 3 -
<PAGE>   5



ITEM 9. UNDERTAKINGS.

        The undersigned Registrant hereby undertakes:

        (a)     To file, during any period in which offers or sales are being
        made, a post-effective amendment to this registration statement:

                        (i) To include any prospectus required by Section
                10(a)(3) of the Securities Act of 1933;

                        (ii) To reflect in the prospectus any facts or events
                arising after the effective date of the Registration Statement
                (or the most recent post-effective amendment thereof) which,
                individually or in the aggregate, represent a fundamental change
                in the information set forth in the Registration Statement.
                Notwithstanding the foregoing, any increase or decrease in
                volume of securities offered (if the total dollar value of
                securities offered would not exceed that which was registered)
                and any deviation from the low or high end of the estimated
                maximum offering range may be reflected in the form of
                prospectus filed with the Commission pursuant to Rule 424(b) if,
                in the aggregate, the changes in volume and price represent no
                more than a 20% change in the maximum aggregate offering price
                set forth in the "Calculation of Registration Fee" table in the
                effective registration statement;

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

                Provided, however, that paragraphs (a)(i) and (a)(ii) do not
        apply if the Registration Statement is on Form S-3 or Form S-8, and 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 Exchange Act
        that are incorporated by reference in the Registration Statement.

        (b)     That, for the purpose of determining any liability under the
        Securities Act of 1933, each such post-effective amendment shall be
        deemed to be a new registration statement relating to the securities
        offered therein, and the offering of such securities at that time shall
        be deemed to be the initial bona fide offering thereof.

        (c)     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.




                                     - 4 -
<PAGE>   6


        The undersigned Registrant hereby undertakes that, for 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 (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to 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.

        The undertaking concerning indemnification is set forth under the
response to Item 6.




                                     - 5 -
<PAGE>   7




                                   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 Linthicum, State of Maryland, on July 23, 1999

                                       CIENA Corporation

                                 By: /S/ PATRICK H. NETTLES, Ph.D.
                                    --------------------------------------
                                    Patrick H. Nettles, Ph.D.
                                    President and Chief Executive Officer

Pursuant to the requirements of the Securities Act of 1933, this Registration
Statement has been signed by the following persons in the capacities and on the
date indicated.

We, the undersigned officers and directors of CIENA Corporation, hereby
severally and individually constitute and appoint Patrick H. Nettles, Joseph R.
Chinnici and Michael O. McCarthy, and each of them, the true and lawful
attorneys and agents of each of us to execute in the name, place and stead of
each of us (individually and in any capacity stated below) any and all
amendments to this Registration Statement on Form S-8, and all instruments
necessary or advisable in connection therewith and to file the same with the
Securities and Exchange Commission, each of said attorneys and agents to have
power to act with or without the other and to have full power and authority to
do and perform in the name and on behalf of each of the undersigned every act
whatsoever necessary or advisable to be done in the premises as fully and to all
intents and purposes as any of the undersigned might or could do in person, and
we hereby ratify and confirm our signatures as they may be signed by our said
attorneys and agents and each of them to any and all such amendment and
amendments.




                                     - 6 -
<PAGE>   8
                             By: /s/ PATRICK H. NETTLES
                                 ----------------------------
                                 Patrick H. Nettles, Ph.D.
                                 President and Chief
                                 Executive Officer

                                 /s/ JOSEPH R. CHINNICI
                                 ----------------------------
                                 Joseph R. Chinnici
                                 Sr. Vice President, Chief Financial Officer
                                 Principal Financial Officer

                                 /s/ ANDREW C. PETRIK
                                 ----------------------------
                                 Andrew C. Petrik
                                 Vice President, Controller and Treasurer
                                 Principal Accounting Officer

                                 /s/ HARVEY B. CASH
                                 ----------------------------
                                 Harvey B. Cash
                                 Director

                                 /s/ BILLY B. OLIVER
                                 ----------------------------
                                 Billy B. Oliver
                                 Director

                                 /s/ MICHAEL J. ZAK
                                 ----------------------------
                                 Michael J. Zak
                                 Director

                                 /s/ STEPHEN P. BRADLEY
                                 ----------------------------
                                 Stephen P. Bradley
                                 Director

                                  EXHIBIT INDEX

Exhibit
Number                        Description
------                        -----------





                                     - 7 -
<PAGE>   9
4.1     Form of Common Stock Certificate (filed as Exhibit 4.1 to the Initial
        Form S-1 and incorporated herein by reference).

4.2     Rights Agreement dated December 29, 1997 (filed as Exhibit 4.2 to the
        Registrant's Form 8-K dated December 29, 1997 and incorporated herein by
        reference).

4.3     Amendment to Rights Agreement (filed as Exhibit 4.3 to the Registrant's
        Form 8-K dated October 14, 1998 and incorporated herein by reference).

5.1     Opinion of Hogan & Hartson L.L.P. regarding the legality of the
        securities being registered.

23.1    Consent of PricewaterhouseCoopers LLP.

23.2    Consent of Hogan & Hartson L.L.P. (included in their opinion filed as
        Exhibit 5.1 hereto).

24.1    Power of Attorney (included on signature page).


                                     - 8 -
[{"type": "S-8", "sequence": "1", "description": "CIENA CORP. FORM S-8", "secsgml_size_bytes": 17537}]
{"company-data": {"conformed-name": "CIENA CORP", "cik": "0000936395", "assigned-sic": "3661", "irs-number": "232725311", "state-of-incorporation": "DE", "fiscal-year-end": "1031"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-83581", "film-number": "99669318"}, "business-address": {"street1": "1201 WINTERSON ROAD", "city": "LINTHICUM", "state": "MD", "zip": "21090", "phone": "4108658500"}, "mail-address": {"street1": "1201 WINTERSON ROAD", "city": "LINTHICUM", "state": "MD", "zip": "21090"}}
1

      As filed with the Securities and Exchange Commission on July 23, 1999

                                                  Registration No. 333-_________

                       SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549

                               ------------------
                                    FORM S-8

                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                                CIENA CORPORATION
             ------------------------------------------------------
             (Exact name of registrant as specified in its charter)

              DELAWARE                                  23-2725311
------------------------------------      --------------------------------------
    (State or other jurisdiction           (I.R.S. employer identification no.)
  of incorporation or organization)

                               1201 WINTERSON ROAD
                               LINTHICUM, MD 21090
                    ----------------------------------------
                    (Address of principal executive offices)

                   OMNIA COMMUNICATIONS, INC. 1997 STOCK PLAN,
                                   AS AMENDED
                   -------------------------------------------
                            (Full title of the plan)

                               MICHAEL O. MCCARTHY
                    VICE PRESIDENT, ASSISTANT GENERAL COUNSEL
                                  AND SECRETARY
                                CIENA CORPORATION
                               1201 WINTERSON ROAD
                               LINTHICUM, MD 21090
                                 (410) 865-8500
-------------------------------------------------------------------------------
(Name, address and telephone number, including area code, of agent for service)

                                    Copy to:
                               AMY BOWERMAN FREED
                             HOGAN & HARTSON L.L.P.
                            111 SOUTH CALVERT STREET
                               BALTIMORE, MD 21202
                                 (410) 659-2700

                         CALCULATION OF REGISTRATION FEE
=============================================================================================================
                                                Proposed              Proposed
  Title of securities      Amount to be      maximum offering     maximum aggregate          Amount of
   to be registered         registered      price per share (1)   offering price (1)    registration fee (1)
-------------------------------------------------------------------------------------------------------------
COMMON STOCK, PAR            755,356             $13.87              $ 10,476,788            $ 2,913
VALUE $.01
=============================================================================================================
(1) The proposed maximum offering price per share is the weighted average
    exercise price of outstanding options. The filing fee is computed under Rule
    457(h)(1) based on the aggregate price at which the options may be
    exercised.
2

                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

        The documents containing the information specified in Part I will be
separately sent or given to employees participating in the Omnia Communications,
Inc. 1997 Stock Plan, As Amended (the "Stock Plan"), as specified by Rule
428(b)(1) of the Securities Act of 1933, as amended (the "Securities Act"). In
accordance with the instructions to Part I of Form S-8, such documents will not
be filed with the Securities and Exchange Commission (the "Commission") either
as part of this Registration Statement or as prospectuses or prospectus
supplements pursuant to Rule 424 of the Securities Act.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.           INCORPORATION OF DOCUMENTS BY REFERENCE.

        The Company hereby incorporates by reference into this Registration
Statement the following documents filed by it with the Commission:

        (a)     The Company's annual report on Form 10-K for the fiscal year
                ended October 31, 1998, filed on December 10, 1998, and amended
                on April 5, 1999;

        (b)     The Company's reports on Form 10-Q filed on February 18, 1999
                and May 21, 1999, the Company's report on Form 8-K filed on
                April 1, 1999, and amended on April 5, 1999, the Company's
                report on Form 8-K filed on April 5, 1999 and the Company's
                report on Form 8-K filed on July 21, 1999.

        (c)     The description of the Company's common stock contained in the
                Company's Registration Statement on Form 8-A, filed with the
                Commission on January 13, 1997;

        In addition, all documents and reports filed by the Company subsequent
to the date hereof pursuant to Sections 13(a), 13(c), 14, or 15(d) of the
Securities Exchange Act, as amended (the "Exchange Act"), prior to the filing of
a post-effective amendment which indicates that all securities offered have been
sold or which deregisters all securities remaining unsold, shall be deemed to be
incorporated by reference in this Registration Statement and to be a part hereof
from the date of filing of such documents. Any statement contained 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 subsequent 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, except as so modified or superseded, to
constitute a part of this Registration Statement.

ITEM 4. DESCRIPTION OF SECURITIES.

        Not applicable (the Common Stock is registered under Section 12(g) of
the Exchange Act)
3

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

        Not applicable.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

        Item 14 of Part II of the Registration Statement of the Registrant on
Form S-1 (Registration No. 333-17729) is hereby incorporated by reference into
this Registration Statement.

                                      * * *

        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 Commission, such
indemnification is against public policy as expressed in the Securities Act and
therefore is unenforceable. In the event that a claim for indemnification
against such liabilities is asserted by such person in connection with the
offering of the Common Stock (other than for 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) 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 of whether such indemnification by it is against public policy as
expressed in the Securities Act and will be governed by the final adjudication
of the issue.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

        Not applicable.

ITEM 8. EXHIBITS.

Exhibit
Number                           Description
------                           -----------

4.1     Form of Common Stock Certificate (filed as Exhibit 4.1 to the Initial
        Form S-1 and incorporated herein by reference).

                                     - 2 -
4

4.2     Rights Agreement dated December 29, 1997 (filed as Exhibit 4.2 to the
        Registrant's Form 8-K dated December 29, 1997 and incorporated herein by
        reference).

4.3     Amendment to Rights Agreement (filed as Exhibit 4.3 to the Registrant's
        Form 8-K dated October 14, 1998 and incorporated herein by reference).

5.1     Opinion of Hogan & Hartson L.L.P. regarding the legality of the
        securities being registered.

23.1    Consent of PricewaterhouseCoopers LLP.

23.2    Consent of Hogan & Hartson L.L.P. (included in their opinion filed as
        Exhibit 5.1 hereto).

24.1    Power of Attorney (included on signature page).

                                     - 3 -
5

ITEM 9. UNDERTAKINGS.

        The undersigned Registrant hereby undertakes:

        (a)     To file, during any period in which offers or sales are being
        made, a post-effective amendment to this registration statement:

                        (i) To include any prospectus required by Section
                10(a)(3) of the Securities Act of 1933;

                        (ii) To reflect in the prospectus any facts or events
                arising after the effective date of the Registration Statement
                (or the most recent post-effective amendment thereof) which,
                individually or in the aggregate, represent a fundamental change
                in the information set forth in the Registration Statement.
                Notwithstanding the foregoing, any increase or decrease in
                volume of securities offered (if the total dollar value of
                securities offered would not exceed that which was registered)
                and any deviation from the low or high end of the estimated
                maximum offering range may be reflected in the form of
                prospectus filed with the Commission pursuant to Rule 424(b) if,
                in the aggregate, the changes in volume and price represent no
                more than a 20% change in the maximum aggregate offering price
                set forth in the "Calculation of Registration Fee" table in the
                effective registration statement;

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

                Provided, however, that paragraphs (a)(i) and (a)(ii) do not
        apply if the Registration Statement is on Form S-3 or Form S-8, and 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 Exchange Act
        that are incorporated by reference in the Registration Statement.

        (b)     That, for the purpose of determining any liability under the
        Securities Act of 1933, each such post-effective amendment shall be
        deemed to be a new registration statement relating to the securities
        offered therein, and the offering of such securities at that time shall
        be deemed to be the initial bona fide offering thereof.

        (c)     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.

                                     - 4 -
6

        The undersigned Registrant hereby undertakes that, for 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 (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to 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.

        The undertaking concerning indemnification is set forth under the
response to Item 6.

                                     - 5 -
7

                                   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 Linthicum, State of Maryland, on July 23, 1999

                                       CIENA Corporation

                                 By: /S/ PATRICK H. NETTLES, Ph.D.
                                    --------------------------------------
                                    Patrick H. Nettles, Ph.D.
                                    President and Chief Executive Officer

Pursuant to the requirements of the Securities Act of 1933, this Registration
Statement has been signed by the following persons in the capacities and on the
date indicated.

We, the undersigned officers and directors of CIENA Corporation, hereby
severally and individually constitute and appoint Patrick H. Nettles, Joseph R.
Chinnici and Michael O. McCarthy, and each of them, the true and lawful
attorneys and agents of each of us to execute in the name, place and stead of
each of us (individually and in any capacity stated below) any and all
amendments to this Registration Statement on Form S-8, and all instruments
necessary or advisable in connection therewith and to file the same with the
Securities and Exchange Commission, each of said attorneys and agents to have
power to act with or without the other and to have full power and authority to
do and perform in the name and on behalf of each of the undersigned every act
whatsoever necessary or advisable to be done in the premises as fully and to all
intents and purposes as any of the undersigned might or could do in person, and
we hereby ratify and confirm our signatures as they may be signed by our said
attorneys and agents and each of them to any and all such amendment and
amendments.

                                     - 6 -
8
                             By: /s/ PATRICK H. NETTLES
                                 ----------------------------
                                 Patrick H. Nettles, Ph.D.
                                 President and Chief
                                 Executive Officer

                                 /s/ JOSEPH R. CHINNICI
                                 ----------------------------
                                 Joseph R. Chinnici
                                 Sr. Vice President, Chief Financial Officer
                                 Principal Financial Officer

                                 /s/ ANDREW C. PETRIK
                                 ----------------------------
                                 Andrew C. Petrik
                                 Vice President, Controller and Treasurer
                                 Principal Accounting Officer

                                 /s/ HARVEY B. CASH
                                 ----------------------------
                                 Harvey B. Cash
                                 Director

                                 /s/ BILLY B. OLIVER
                                 ----------------------------
                                 Billy B. Oliver
                                 Director

                                 /s/ MICHAEL J. ZAK
                                 ----------------------------
                                 Michael J. Zak
                                 Director

                                 /s/ STEPHEN P. BRADLEY
                                 ----------------------------
                                 Stephen P. Bradley
                                 Director

                                  EXHIBIT INDEX

Exhibit
Number                        Description
------                        -----------

                                     - 7 -
9
4.1     Form of Common Stock Certificate (filed as Exhibit 4.1 to the Initial
        Form S-1 and incorporated herein by reference).

4.2     Rights Agreement dated December 29, 1997 (filed as Exhibit 4.2 to the
        Registrant's Form 8-K dated December 29, 1997 and incorporated herein by
        reference).

4.3     Amendment to Rights Agreement (filed as Exhibit 4.3 to the Registrant's
        Form 8-K dated October 14, 1998 and incorporated herein by reference).

5.1     Opinion of Hogan & Hartson L.L.P. regarding the legality of the
        securities being registered.

23.1    Consent of PricewaterhouseCoopers LLP.

23.2    Consent of Hogan & Hartson L.L.P. (included in their opinion filed as
        Exhibit 5.1 hereto).

24.1    Power of Attorney (included on signature page).

                                     - 8 -