<PAGE>   1

   As filed with the Securities and Exchange Commission on December 14, 1999
                                                     Registration No. 333-______
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

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

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      Under
                           The Securities Act of 1933

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

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

<TABLE>
<S>                                                          <C>
            DELAWARE                                             94-3222307
  (State or other jurisdiction                                 (IRS Employer
of incorporation or organization)                            Identification No.)
</TABLE>

                                  700 BAY ROAD
                         REDWOOD CITY, CALIFORNIA 94063
               (Address of principal executive offices) (Zip Code)

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

                                 HEARTPORT, INC.
                       1999 SUPPLEMENTAL STOCK OPTION PLAN
                          EMPLOYEE STOCK PURCHASE PLAN
                            (Full title of the Plans)

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

                                 CASEY M. TANSEY
                      PRESIDENT AND CHIEF EXECUTIVE OFFICER
                                 HEARTPORT, INC.
                                  700 BAY ROAD
                         REDWOOD CITY, CALIFORNIA 94063
                     (Name and address of agent for service)
                                 (650) 306-7900
          (Telephone number, including area code, of agent for service)


<TABLE>
<CAPTION>
                                       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(2)          Price(2)             Fee
        -------------------               -------------   ----------------   ------------------   ------------
<S>                                         <C>                <C>                  <C>                <C>
1999 Supplemental Stock Option Plan
     Options                                1,500,000           N/A                 N/A                N/A
     Common Stock (par value $.001)         1,500,000          $4.91             $7,365,000         $1,944.36

Employee Stock Purchase Plan
     Options                                  126,153           N/A                 N/A                N/A
     Common Stock (par value $.001)           126,153          $4.91             $619,411.23          $163.53
==============================================================================================================
</TABLE>

(1)  This Registration Statement shall also cover any additional shares of
     Common Stock which become issuable under the 1999 Supplemental Stock Option
     Plan and the Employee Stock Purchase Plan by reason of any stock dividend,
     stock split, recapitalization or other similar transaction effected without
     the receipt of consideration which results in an increase in the number of
     the outstanding shares of Common Stock of Heartport, Inc.

(2)  Calculated solely for purposes of this offering under Rule 457(h) of the
     Securities Act of 1933, as amended, on the basis of the fair market value
     per share of Common Stock of Heartport, Inc. on December 9, 1999.

<PAGE>   2

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3. Incorporation of Documents by Reference

     Heartport, Inc. (the "Registrant") hereby incorporates by reference into
this Registration Statement the following documents previously filed with the
Securities and Exchange Commission (the "SEC"):

     (a)  The Registrant's Annual Report on Form 10-K for the fiscal year ended
          December 31, 1998, as filed with the SEC on March 30, 1999;

     (b)  The Registrant's Quarterly Report on Form 10-Q for the quarter ended
          March 31, 1999, as filed with the SEC on May 17, 1999;

     (c)  The Registrant's Quarterly Report on Form 10-Q for the quarter ended
          June 30, 1999, as filed with the SEC on August 13, 1999;

     (d)  The Registrant's Quarterly Report on Form 10-Q for the quarter ended
          September 30, 1999, as filed with the SEC on November 15, 1999; and

     (e)  The Registrant's Registration Statement No. 0-28266 on Form 8-A filed
          with the SEC on April 25, 1996, pursuant to Section 12 of the
          Securities Exchange Act of 1934, as amended (the "1934 Act"), in which
          there is described the terms, rights and provisions applicable to the
          Registrant's outstanding Common Stock.

     All reports and definitive proxy or information statements filed pursuant
to Section 13(a), 13(c), 14 or 15(d) of the 1934 Act after the date of this
Registration Statement and prior to the filing of a post-effective amendment
which indicates that all securities offered hereby have been sold or which
deregisters all securities then remaining unsold shall be deemed to be
incorporated by reference into this Registration Statement and to be a part
hereof from the date of filing of such documents.

Item 4. Description of Securities

     Not Applicable.

Item 5. Interests of Named Experts and Counsel

     Not Applicable.

Item 6. Indemnification of Directors and Officers

     Section 145 of the Delaware General Corporation Law authorizes a court to
award or a corporation's Board of Directors to grant indemnification to
directors and officers in terms sufficiently broad to permit such
indemnification under certain circumstances for liabilities (including
reimbursement for expenses incurred) arising under the 1933 Act. The
Registrant's Bylaws provide for mandatory indemnification of its directors and
officers and permissible indemnification of employees and other agents to the
maximum extent permitted by the Delaware General Corporation Law. The
Registrant's Certificate of Incorporation provides that, pursuant to Delaware
law, its directors shall not be liable for monetary damages for breach of their
fiduciary duty as directors to the Registrant and its stockholders. This
provision in the Certificate of Incorporation does not eliminate the fiduciary
duty of the directors, and, in appropriate circumstances, equitable remedies
such as injunctive or other forms of non-monetary relief will remain available
under Delaware law. In addition, each director will continue to be subject to
liability for breach of the director's duty of loyalty to the Registrant for
acts or omissions not in good faith or involving intentional misconduct, for
knowing violations of law, for actions leading to improper personal benefit to
the director and for payment of dividends or


                                      II-2

<PAGE>   3

approval of stock repurchases or redemptions that are unlawful under Delaware
law. The provision also does not affect a director's responsibilities under any
other law, such as the federal securities laws or state or federal environmental
laws. The Registrant has entered into Indemnification Agreements with its
officers and directors. The Indemnification Agreements provide the Registrant's
officers and directors with further indemnification to the maximum extent
permitted by the Delaware General Corporation Law.


                                      II-3

<PAGE>   4

Item 7. Exemption from Registration Claimed

     Not Applicable.

Item 8. Exhibits

<TABLE>
<CAPTION>
Exhibit
Number         Exhibit
-------        -------
<S>            <C>
   4           Instruments Defining Rights of Stockholders. Reference is made to
               Registrant's Registration Statement No. 0-28266 on Form 8-A, which
               is incorporated herein by reference pursuant to Item 3(e) of this
               Registration Statement.

   5           Opinion and consent of Gunderson Dettmer Stough Villeneuve Franklin
               & Hachigian, LLP.

   23.1        Consent of Ernst & Young LLP, Independent Auditors.

   23.2        Consent of Gunderson Dettmer Stough Villeneuve Franklin & Hachigian,
               LLP is contained in Exhibit 5.

   24          Power of Attorney. Reference is made to page II-5 of this Registration
               Statement.
</TABLE>


Item 9. Undertakings

     A.   The undersigned Registrant hereby undertakes: (1) to file, during any
period in which offers or sales are being made, a post-effective amendment to
this Registration Statement (i) to include any prospectus required by Section
10(a)(3) of the 1933 Act, (ii) to reflect in the prospectus any facts or events
arising after the effective date of this Registration Statement (or the most
recent post-effective amendment thereof) which, individually or in the
aggregate, represent a fundamental change in the information set forth in this
Registration Statement and (iii) to include any material information with
respect to the plan of distribution not previously disclosed in this
Registration Statement or any material change to such information in this
Registration Statement; provided, however, that clauses (1)(i) and (1)(ii) shall
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 1934 Act that are
incorporated by reference into this Registration Statement; (2) that for the
purpose of determining any liability under the 1933 Act each such post-effective
amendment shall be deemed to be a new registration statement relating to the
securities offered therein and the offering of such securities at that time
shall be deemed to be the initial bona fide offering thereof and (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 Registrant's 1999
Supplemental Stock Option Plan and the Employee Stock Purchase Plan.

     B.   The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the 1933 Act, each filing of the Registrant's
annual report pursuant to Section 13(a) or Section 15(d) of the 1934 Act that is
incorporated by reference into this Registration Statement shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

     C.   Insofar as indemnification for liabilities arising under the 1933 Act
may be permitted to directors, officers or controlling persons of the Registrant
pursuant to the indemnification provisions summarized in Item 6 or otherwise,
the Registrant has been advised that, in the opinion of the SEC, such
indemnification is against public policy as expressed in the 1933 Act, and is,
therefore, unenforceable. In the event that a claim for indemnification against
such liabilities (other than the payment by the Registrant of expenses incurred
or paid by a director, officer or controlling person of the Registrant in the
successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the 1933 Act and will be governed by the final
adjudication of such issue.


                                      II-4

<PAGE>   5

                                   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 to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Redwood City, State of California on this 13th
day of December, 1999.

                                        HEARTPORT, INC.


                                        By: /s/ CASEY M. TANSEY
                                           -------------------------------------
                                           Casey M. Tansey
                                           President and Chief Executive Officer


                                POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS:

     That the undersigned officers and directors of Heartport, Inc., a Delaware
corporation, do hereby constitute and appoint Casey M. Tansey and Rebecca L.
Kuhn, and either of them, the lawful attorneys-in-fact and agents with full
power and authority to do any and all acts and things and to execute any and all
instruments which said attorneys and agents, and either one of them, determine
may be necessary or advisable or required to enable said corporation to comply
with the Securities Act of 1933, as amended, and any rules or regulations or
requirements of the Securities and Exchange Commission in connection with this
Registration Statement. Without limiting the generality of the foregoing power
and authority, the powers granted include the power and authority to sign the
names of the undersigned officers and directors in the capacities indicated
below to this Registration Statement, to any and all amendments, both
pre-effective and post-effective, and supplements to this Registration
Statement, and to any and all instruments or documents filed as part of or in
conjunction with this Registration Statement or amendments or supplements
thereof, and either of the undersigned hereby ratifies and confirms that all
said attorneys and agents, or either one of them, shall do or cause to be done
by virtue hereof. This Power of Attorney may be signed in several counterparts.

     IN WITNESS WHEREOF, each of the undersigned has executed this Power of
Attorney as of the date indicated.

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

<TABLE>
<CAPTION>
Signature                               Title                        Date
---------                               -----                        ----
<S>                          <C>                               <C>
/s/ CASEY M. TANSEY          President, Chief Executive        December 13, 1999
---------------------------  Officer and Director
Casey M. Tansey              (Principal Executive Officer)
</TABLE>


                                      II-5

<PAGE>   6

<TABLE>
<CAPTION>
Signature                                     Title                        Date
---------                                     -----                        ----
<S>                                <C>                               <C>
/s/ REBECCA L. KUHN                Assistant Corporate Secretary     December 13, 1999
--------------------------------   Treasurer, and Director of
Rebecca L. Kuhn                    Finance (Principal Financial
                                   and Accounting Officer)


/s/ FRANK M. FISCHER               Director                          December 13, 1999
--------------------------------
Frank M. Fischer


/s/ ROBERT V. GUNDERSON, JR.       Director                          December 13, 1999
--------------------------------
Robert V. Gunderson, Jr.


/s/ JOSEPH S. LACOB                Director                          December 13, 1999
--------------------------------
Joseph S. Lacob


/s/ JOHN H. STEVENS, M.D.          Director                          December 13, 1999
--------------------------------
John H. Stevens, M.D.


/s/ WESLEY D. STERMAN, M.D.        Director                          December 13, 1999
--------------------------------
Wesley D. Sterman, M.D.


/s/ STEVEN C. WHEELWRIGHT, Ph.D.   Director                         December 13, 1999
--------------------------------
Steven C. Wheelwright, Ph.D.
</TABLE>


                                      II-6

<PAGE>   7

                                  EXHIBIT INDEX

<TABLE>
<CAPTION>
Exhibit
Number         Exhibit
-------        -------
<S>            <C>
   4           Instruments Defining Rights of Stockholders. Reference is made to
               Registrant's Registration Statement No. 0-28266 on Form 8-A, which
               is incorporated herein by reference pursuant to Item 3(e) of this
               Registration Statement.

   5           Opinion and consent of Gunderson Dettmer Stough Villeneuve Franklin
               & Hachigian, LLP.

   23.1        Consent of Ernst & Young LLP, Independent Auditors.

   23.2        Consent of Gunderson Dettmer Stough Villeneuve Franklin & Hachigian,
               LLP is contained in Exhibit 5.

   24          Power of Attorney. Reference is made to page II-5 of this Registration
               Statement.
</TABLE>
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 17822}]
{"company-data": {"conformed-name": "HEARTPORT INC", "cik": "0001009871", "assigned-sic": "3841", "irs-number": "943222307", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-92699", "film-number": "99774009"}, "business-address": {"street1": "200 CHESAPEAKE DR", "city": "REDWOOD CITY", "state": "CA", "zip": "94063", "phone": "4153067900"}, "mail-address": {"street1": "200 CHESAPEAKE DRIVE", "city": "REDWOOD CITY", "state": "CA", "zip": "94063"}}
1

   As filed with the Securities and Exchange Commission on December 14, 1999
                                                     Registration No. 333-______
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

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

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      Under
                           The Securities Act of 1933

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

                                 HEARTPORT, INC.
             (Exact name of registrant as specified in its charter)
DELAWARE                                             94-3222307
  (State or other jurisdiction                                 (IRS Employer
of incorporation or organization)                            Identification No.)
700 BAY ROAD
                         REDWOOD CITY, CALIFORNIA 94063
               (Address of principal executive offices) (Zip Code)

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

                                 HEARTPORT, INC.
                       1999 SUPPLEMENTAL STOCK OPTION PLAN
                          EMPLOYEE STOCK PURCHASE PLAN
                            (Full title of the Plans)

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

                                 CASEY M. TANSEY
                      PRESIDENT AND CHIEF EXECUTIVE OFFICER
                                 HEARTPORT, INC.
                                  700 BAY ROAD
                         REDWOOD CITY, CALIFORNIA 94063
                     (Name and address of agent for service)
                                 (650) 306-7900
          (Telephone number, including area code, of agent for service)
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(2)          Price(2)             Fee
        -------------------               -------------   ----------------   ------------------   ------------
1999 Supplemental Stock Option Plan
     Options                                1,500,000           N/A                 N/A                N/A
     Common Stock (par value $.001)         1,500,000          $4.91             $7,365,000         $1,944.36

Employee Stock Purchase Plan
     Options                                  126,153           N/A                 N/A                N/A
     Common Stock (par value $.001)           126,153          $4.91             $619,411.23          $163.53
==============================================================================================================
(1)  This Registration Statement shall also cover any additional shares of
     Common Stock which become issuable under the 1999 Supplemental Stock Option
     Plan and the Employee Stock Purchase Plan by reason of any stock dividend,
     stock split, recapitalization or other similar transaction effected without
     the receipt of consideration which results in an increase in the number of
     the outstanding shares of Common Stock of Heartport, Inc.

(2)  Calculated solely for purposes of this offering under Rule 457(h) of the
     Securities Act of 1933, as amended, on the basis of the fair market value
     per share of Common Stock of Heartport, Inc. on December 9, 1999.
2

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3. Incorporation of Documents by Reference

     Heartport, Inc. (the "Registrant") hereby incorporates by reference into
this Registration Statement the following documents previously filed with the
Securities and Exchange Commission (the "SEC"):

     (a)  The Registrant's Annual Report on Form 10-K for the fiscal year ended
          December 31, 1998, as filed with the SEC on March 30, 1999;

     (b)  The Registrant's Quarterly Report on Form 10-Q for the quarter ended
          March 31, 1999, as filed with the SEC on May 17, 1999;

     (c)  The Registrant's Quarterly Report on Form 10-Q for the quarter ended
          June 30, 1999, as filed with the SEC on August 13, 1999;

     (d)  The Registrant's Quarterly Report on Form 10-Q for the quarter ended
          September 30, 1999, as filed with the SEC on November 15, 1999; and

     (e)  The Registrant's Registration Statement No. 0-28266 on Form 8-A filed
          with the SEC on April 25, 1996, pursuant to Section 12 of the
          Securities Exchange Act of 1934, as amended (the "1934 Act"), in which
          there is described the terms, rights and provisions applicable to the
          Registrant's outstanding Common Stock.

     All reports and definitive proxy or information statements filed pursuant
to Section 13(a), 13(c), 14 or 15(d) of the 1934 Act after the date of this
Registration Statement and prior to the filing of a post-effective amendment
which indicates that all securities offered hereby have been sold or which
deregisters all securities then remaining unsold shall be deemed to be
incorporated by reference into this Registration Statement and to be a part
hereof from the date of filing of such documents.

Item 4. Description of Securities

     Not Applicable.

Item 5. Interests of Named Experts and Counsel

     Not Applicable.

Item 6. Indemnification of Directors and Officers

     Section 145 of the Delaware General Corporation Law authorizes a court to
award or a corporation's Board of Directors to grant indemnification to
directors and officers in terms sufficiently broad to permit such
indemnification under certain circumstances for liabilities (including
reimbursement for expenses incurred) arising under the 1933 Act. The
Registrant's Bylaws provide for mandatory indemnification of its directors and
officers and permissible indemnification of employees and other agents to the
maximum extent permitted by the Delaware General Corporation Law. The
Registrant's Certificate of Incorporation provides that, pursuant to Delaware
law, its directors shall not be liable for monetary damages for breach of their
fiduciary duty as directors to the Registrant and its stockholders. This
provision in the Certificate of Incorporation does not eliminate the fiduciary
duty of the directors, and, in appropriate circumstances, equitable remedies
such as injunctive or other forms of non-monetary relief will remain available
under Delaware law. In addition, each director will continue to be subject to
liability for breach of the director's duty of loyalty to the Registrant for
acts or omissions not in good faith or involving intentional misconduct, for
knowing violations of law, for actions leading to improper personal benefit to
the director and for payment of dividends or

                                      II-2
3

approval of stock repurchases or redemptions that are unlawful under Delaware
law. The provision also does not affect a director's responsibilities under any
other law, such as the federal securities laws or state or federal environmental
laws. The Registrant has entered into Indemnification Agreements with its
officers and directors. The Indemnification Agreements provide the Registrant's
officers and directors with further indemnification to the maximum extent
permitted by the Delaware General Corporation Law.

                                      II-3
4

Item 7. Exemption from Registration Claimed

     Not Applicable.

Item 8. Exhibits
Exhibit
Number         Exhibit
-------        -------
4           Instruments Defining Rights of Stockholders. Reference is made to
               Registrant's Registration Statement No. 0-28266 on Form 8-A, which
               is incorporated herein by reference pursuant to Item 3(e) of this
               Registration Statement.

   5           Opinion and consent of Gunderson Dettmer Stough Villeneuve Franklin
               & Hachigian, LLP.

   23.1        Consent of Ernst & Young LLP, Independent Auditors.

   23.2        Consent of Gunderson Dettmer Stough Villeneuve Franklin & Hachigian,
               LLP is contained in Exhibit 5.

   24          Power of Attorney. Reference is made to page II-5 of this Registration
               Statement.
Item 9. Undertakings

     A.   The undersigned Registrant hereby undertakes: (1) to file, during any
period in which offers or sales are being made, a post-effective amendment to
this Registration Statement (i) to include any prospectus required by Section
10(a)(3) of the 1933 Act, (ii) to reflect in the prospectus any facts or events
arising after the effective date of this Registration Statement (or the most
recent post-effective amendment thereof) which, individually or in the
aggregate, represent a fundamental change in the information set forth in this
Registration Statement and (iii) to include any material information with
respect to the plan of distribution not previously disclosed in this
Registration Statement or any material change to such information in this
Registration Statement; provided, however, that clauses (1)(i) and (1)(ii) shall
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 1934 Act that are
incorporated by reference into this Registration Statement; (2) that for the
purpose of determining any liability under the 1933 Act each such post-effective
amendment shall be deemed to be a new registration statement relating to the
securities offered therein and the offering of such securities at that time
shall be deemed to be the initial bona fide offering thereof and (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 Registrant's 1999
Supplemental Stock Option Plan and the Employee Stock Purchase Plan.

     B.   The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the 1933 Act, each filing of the Registrant's
annual report pursuant to Section 13(a) or Section 15(d) of the 1934 Act that is
incorporated by reference into this Registration Statement shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

     C.   Insofar as indemnification for liabilities arising under the 1933 Act
may be permitted to directors, officers or controlling persons of the Registrant
pursuant to the indemnification provisions summarized in Item 6 or otherwise,
the Registrant has been advised that, in the opinion of the SEC, such
indemnification is against public policy as expressed in the 1933 Act, and is,
therefore, unenforceable. In the event that a claim for indemnification against
such liabilities (other than the payment by the Registrant of expenses incurred
or paid by a director, officer or controlling person of the Registrant in the
successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the 1933 Act and will be governed by the final
adjudication of such issue.

                                      II-4
5

                                   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 to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Redwood City, State of California on this 13th
day of December, 1999.

                                        HEARTPORT, INC.

                                        By: /s/ CASEY M. TANSEY
                                           -------------------------------------
                                           Casey M. Tansey
                                           President and Chief Executive Officer

                                POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS:

     That the undersigned officers and directors of Heartport, Inc., a Delaware
corporation, do hereby constitute and appoint Casey M. Tansey and Rebecca L.
Kuhn, and either of them, the lawful attorneys-in-fact and agents with full
power and authority to do any and all acts and things and to execute any and all
instruments which said attorneys and agents, and either one of them, determine
may be necessary or advisable or required to enable said corporation to comply
with the Securities Act of 1933, as amended, and any rules or regulations or
requirements of the Securities and Exchange Commission in connection with this
Registration Statement. Without limiting the generality of the foregoing power
and authority, the powers granted include the power and authority to sign the
names of the undersigned officers and directors in the capacities indicated
below to this Registration Statement, to any and all amendments, both
pre-effective and post-effective, and supplements to this Registration
Statement, and to any and all instruments or documents filed as part of or in
conjunction with this Registration Statement or amendments or supplements
thereof, and either of the undersigned hereby ratifies and confirms that all
said attorneys and agents, or either one of them, shall do or cause to be done
by virtue hereof. This Power of Attorney may be signed in several counterparts.

     IN WITNESS WHEREOF, each of the undersigned has executed this Power of
Attorney as of the date indicated.

     Pursuant to the requirements of the Securities Act of 1933, as amended,
this Registration Statement has been signed below by the following persons in
the capacities and on the dates indicated.
Signature                               Title                        Date
---------                               -----                        ----
/s/ CASEY M. TANSEY          President, Chief Executive        December 13, 1999
---------------------------  Officer and Director
Casey M. Tansey              (Principal Executive Officer)
II-5
6
Signature                                     Title                        Date
---------                                     -----                        ----
/s/ REBECCA L. KUHN                Assistant Corporate Secretary     December 13, 1999
--------------------------------   Treasurer, and Director of
Rebecca L. Kuhn                    Finance (Principal Financial
                                   and Accounting Officer)

/s/ FRANK M. FISCHER               Director                          December 13, 1999
--------------------------------
Frank M. Fischer

/s/ ROBERT V. GUNDERSON, JR.       Director                          December 13, 1999
--------------------------------
Robert V. Gunderson, Jr.

/s/ JOSEPH S. LACOB                Director                          December 13, 1999
--------------------------------
Joseph S. Lacob

/s/ JOHN H. STEVENS, M.D.          Director                          December 13, 1999
--------------------------------
John H. Stevens, M.D.

/s/ WESLEY D. STERMAN, M.D.        Director                          December 13, 1999
--------------------------------
Wesley D. Sterman, M.D.

/s/ STEVEN C. WHEELWRIGHT, Ph.D.   Director                         December 13, 1999
--------------------------------
Steven C. Wheelwright, Ph.D.
II-6
7

                                  EXHIBIT INDEX
Exhibit
Number         Exhibit
-------        -------
4           Instruments Defining Rights of Stockholders. Reference is made to
               Registrant's Registration Statement No. 0-28266 on Form 8-A, which
               is incorporated herein by reference pursuant to Item 3(e) of this
               Registration Statement.

   5           Opinion and consent of Gunderson Dettmer Stough Villeneuve Franklin
               & Hachigian, LLP.

   23.1        Consent of Ernst & Young LLP, Independent Auditors.

   23.2        Consent of Gunderson Dettmer Stough Villeneuve Franklin & Hachigian,
               LLP is contained in Exhibit 5.

   24          Power of Attorney. Reference is made to page II-5 of this Registration
               Statement.