Document:

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                                                                    EXHIBIT 10.1

                                VOTING AGREEMENT

      This Voting Agreement (the "Agreement") is made and entered into as of May
12, 2004, between RITA Medical Systems, Inc., a Delaware corporation ("Parent"),
Horizon Medical Products, Inc., a Georgia corporation (the "Company"), and the
undersigned shareholder of the Company ("Holder").

                                    RECITALS

      Pursuant to an Agreement and Plan of Merger dated as of May 12, 2004 (the
"Merger Agreement") by and among Parent, Hornet Acquisition Corp. a Delaware
corporation and wholly-owned subsidiary of Parent ("Merger Sub"), and the
Company, Merger Sub is merging with and into the Company (the "Merger") and the
Company, as the surviving corporation of the Merger, will thereby become a
wholly-owned subsidiary of Parent. Concurrently with the execution and delivery
of the Merger Agreement and as a condition and inducement to Parent and Merger
Sub to enter into the Merger Agreement, Parent has required that Holder enter
into this Agreement. The Holder is the record and beneficial owner of such
number of shares of the outstanding Common Stock, $0.001 par value per share, of
the Company as is indicated beneath Holder's signature on the last page of this
Agreement (the "Shares").

                                    AGREEMENT

      The parties agree as follows:

      1. AGREEMENT TO RETAIN SHARES.

            (a) TRANSFER AND ENCUMBRANCE. (1) Except as contemplated by the
Merger Agreement, and except as provided in Section 1(b) below, during the
period beginning on the date hereof and ending on the earlier to occur of (i)
the Effective Time (as defined in the Merger Agreement), and (ii) the Expiration
Date (as defined below), Holder agrees not to, directly or indirectly, transfer
(except as may be specifically required by court order), sell, exchange, tender,
pledge, assign, contribute to the capital of any entity, hypothecate or
otherwise dispose of (including by merger, consolidation or otherwise by
operation of law) or encumber the Shares or any New Shares (as defined below),
or to, directly or indirectly, make any offer or agreement relating thereto, (2)
Holder agrees not to, directly or indirectly, grant any proxies or powers of
attorney, deposit any of such Holder's Shares into a voting trust or enter into
a voting agreement with respect to any of such Holder's Shares, or enter into
any agreement or arrangement providing for any of the actions described in this
clause (2) and (3) Holder agrees not to, directly or indirectly, take any action
that could reasonably be expected to have the effect of preventing or disabling
Holder from performing Holder's obligations under this Agreement at any time
prior to the earlier to occur of (i) the Effective Time, and (ii) the Expiration
Date. As used herein, the term "Expiration Date" shall mean the earlier to occur
of (i) the date of termination of the Merger Agreement in accordance with the
terms and provisions thereof and (ii) the date on which the Company's Board of
Directors withdraws or modifies in a manner adverse to Parent or Merger Sub the
Company Recommendation (as defined in the Merger Agreement) in accordance with
the requirements of the second sentence of Section 4.3(e) of the Merger
Agreement.

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            (b) PERMITTED TRANSFERS. Section 1(a) shall not prohibit a transfer
of Shares or New Shares by Holder (i) in accordance with the provisions of Rule
144 applicable to Holder, (ii) if Holder is an individual (A) to any member of
Holder's immediate family, or to a trust for the benefit of Holder or any member
of Holder's immediate family, or (B) upon the death of Holder, or (iii) if
Holder is a partnership or limited liability company, to one or more partners or
members of Holder or to an affiliated Person under common control with Holder;
provided, however, that a transfer referred to in clauses (ii) and (iii) of this
sentence shall be permitted only if, as a precondition to such transfer, the
transferee agrees in writing to be bound by all of the terms of this Agreement.

            (c) NEW SHARES. Holder agrees that any shares of capital stock of
the Company that Holder purchases or with respect to which Holder otherwise
acquires record or beneficial ownership after the date of this Agreement and
prior to the earlier to occur of (i) the Effective Time and (ii) the Expiration
Date ("New Shares") shall be subject to the terms and conditions of this
Agreement to the same extent as if they constituted Shares. Holder further
agrees that any shares of capital stock of Parent that Holder purchases or with
respect to which Holder otherwise acquires record or beneficial ownership after
the date of this Agreement and prior to the earlier to occur of (i) the record
date for Parent's 2005 annual meeting of stockholders and (ii) the Expiration
Date (including without limitation shares of capital stock of Parent acquired by
Holder as a result of the Merger) shall be subject to the terms and conditions
of Section 2(b) of this Agreement.

            (d) STOP TRANSFER. From and after the date of this Agreement through
the term of this Agreement, the Company will not register or otherwise recognize
the transfer (book-entry or otherwise) of any Shares or any certificate or
uncertificated interest representing any of Holder's Shares, except as permitted
by, and in accordance with, Section 1(b).

      2. AGREEMENT TO VOTE SHARES.

            (a) Until the earlier to occur of (i) the Effective Time and (ii)
the Expiration Date, at every meeting of the shareholders of the Company called
with respect to any of the following, and at every adjournment thereof, and on
every action or approval by written consent of the shareholders of the Company
with respect to any of the following, Holder shall vote or consent the Shares
and any New Shares (i) in favor of approval of the Merger Agreement and the
Merger and (ii) against any proposal for any recapitalization, merger, sale of
assets or other business combination (other than the Merger) between the Company
and any person or entity other than Parent or any other action or agreement that
could reasonably be expected to result in a breach of any covenant,
representation or warranty or any other obligation or agreement of the Company
under the Merger Agreement or Holder under this Agreement or which could
reasonably be expected to result in any of the conditions to the Company's
obligations under the Merger Agreement not being fulfilled. This Agreement is
intended to bind Holder as a shareholder of the Company only with respect to the
specific matters set forth herein. Except as set forth in clauses (i) and (ii)
of this Section 2, Holder shall not be restricted from voting in favor of,
against or abstaining with respect to any other matter presented to the
shareholders of the Company.

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            (b) At each of the 2004 and 2005 annual meeting of stockholders of
Parent, and at any adjournment or postponement of either such meeting, Holder
shall vote all shares of capital stock of Parent owned beneficially or of record
by Holder as of the record date for each such annual meeting in favor of the
election of the nominees for director recommended for election by the Board of
Directors of Parent; provided, however, that Holder shall have no obligation
under this Section 2(b) in the event that the Expiration Date occurs prior to
either such annual meeting of stockholders; provided further, that Holder shall
have no obligation under this Section 2(b) with respect to the 2005 annual
meeting of stockholders of Parent if (i) the individual designated by the
Company pursuant to section 5.17(a) of the Merger Agreement to serve as a Class
II director of Parent is willing, able and qualified to serve as a director of
Parent and is not one of the nominees the Board of Directors of Parent
recommends for election at the 2005 annual meeting of stockholders of Parent or
(ii) Parent's compensation policy with respect to non-employee directors is
modified in any material respect prior to the 2005 annual meeting of
stockholders of Parent. Notwithstanding the foregoing, nothing in this
Agreement, including without limitation this Section 2(b), shall restrict
Holder's ability to sell, transfer or otherwise dispose of shares of the capital
stock of Parent following the Effective Time, and no transferee of shares of the
capital stock of Parent beneficially owned by Holder shall have any obligation
under this Agreement after the Effective Time.

      3. IRREVOCABLE PROXY. Concurrently with the execution of this Agreement,
Holder agrees to deliver to Parent a proxy in the form attached hereto as
Exhibit A (the "Proxy"), which shall be irrevocable to the extent provided in
the Georgia Business Corporation Code covering the Shares and New Shares.

      4. REPRESENTATIONS, WARRANTIES AND COVENANTS OF HOLDER. Holder hereby
represents, warrants and covenants to Parent that Holder (i) is the record and
beneficial owner of the Shares, which, at the date of this Agreement and at all
times up until the earlier to occur of (A) the Effective Time, and (B) the
Expiration Date, will be free and clear of any liens, claims, options, charges
or other encumbrances, and (ii) does not own of record or beneficially any
shares of capital stock of the Company other than the Shares (excluding shares
as to which Holder currently disclaims beneficial ownership in accordance with
applicable law). Holder has the legal capacity, power and authority to enter
into and perform all of Holder's under this Agreement (including under the
Proxy). This Agreement (including the Proxy) has been duly and validly executed
and delivered by Holder and constitutes a valid and binding agreement of Holder,
enforceable against Holder in accordance with its terms, subject to (a) laws of
general application relating to bankruptcy, insolvency and the relief of debtors
and (b) rules of law governing specific performance, injunctive relief and other
equitable remedies. [IF HOLDER IS MARRIED AND HOLDER'S SHARES CONSTITUTE
COMMUNITY PROPERTY, THIS AGREEMENT (INCLUDING THE PROXY) HAS BEEN DULY
AUTHORIZED, EXECUTED AND DELIVERED BY, AND CONSTITUTES A VALID AND BINDING
AGREEMENT OF, HOLDER'S SPOUSE, ENFORCEABLE AGAINST SUCH PERSON IN ACCORDANCE
WITH ITS TERMS.] [DELETE IF INAPPLICABLE.]

      5. ADDITIONAL DOCUMENTS. Holder hereby covenants and agrees to execute and
deliver any additional documents reasonably necessary to carry out the purpose
and intent of this Agreement.

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      6. CONSENT AND WAIVER. Holder hereby gives any consents or waivers that
are reasonably required for the consummation of the Merger under the terms of
any agreement to which Holder is a party or pursuant to any rights Holder may
have.

      7. TERMINATION. This Agreement and the Proxy delivered in connection
herewith shall terminate and shall have no further force or effect as of the
earlier to occur of (i) the Expiration Date and (ii) the date following the date
of the 2005 annual meeting of stockholders of Parent, including any adjournment
or postponement thereof.

      8. FIDUCIARY DUTIES. Notwithstanding anything in this Agreement to the
contrary: (i) Holder makes no agreement or understanding herein in any capacity
other than in Holder's capacity as a record holder and beneficial owner of the
Shares, (ii) nothing in this Agreement shall be construed to limit or affect any
action or inaction by Holder, or any officer, partner, member or employee, as
applicable, of Holder, serving on the Company's Board of Directors acting in
such person's capacity as a director or fiduciary of the Company, and (iii)
Holder shall have no liability to Parent, Merger Sub or any of their respective
affiliates under this Agreement as a result of any action or inaction by Holder,
or any officer, partner, member or employee, as applicable, of Holder, serving
on the Company's Board of Directors acting in such person's capacity as a
director or fiduciary of the Company.

      9. MISCELLANEOUS.

            (a) AMENDMENTS AND WAIVERS. Any term of this Agreement may be
amended or waived with the written consent of the parties or their respective
successors and assigns. Any amendment or waiver effected in accordance with this
Section 9(a) shall be binding upon the parties and their respective successors
and assigns.

            (b) GOVERNING LAW. This Agreement and all acts and transactions
pursuant hereto and the rights and obligations of the parties hereto shall be
governed, construed and interpreted in accordance with the laws of Delaware,
without giving effect to principles of conflicts of law.

            (c) COUNTERPARTS. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original and all of which
together shall constitute one instrument.

            (d) TITLES AND SUBTITLES. The titles and subtitles used in this
Agreement are used for convenience only and are not to be considered in
construing or interpreting this Agreement.

            (e) NOTICES. Any notice required or permitted by this Agreement
shall be in writing and shall be deemed sufficient upon receipt, when delivered
personally or by courier, overnight delivery service or confirmed facsimile, or
72 hours after being deposited in the regular mail as certified or registered
mail (airmail if sent internationally) with postage prepaid, if such notice is
addressed to the party to be notified at such party's address or facsimile
number as set forth below, or as subsequently modified by written notice.

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            (f) SEVERABILITY. If one or more provisions of this Agreement are
held to be unenforceable under applicable law, the parties agree to renegotiate
such provision in good faith, in order to maintain the economic position enjoyed
by each party as close as possible to that under the provision rendered
unenforceable. In the event that the parties cannot reach a mutually agreeable
and enforceable replacement for such provision, then (i) such provision shall be
excluded from this Agreement, (ii) the balance of the Agreement shall be
interpreted as if such provision were so excluded and (iii) the balance of the
Agreement shall be enforceable in accordance with its terms.

            (g) SPECIFIC PERFORMANCE. Each of the parties hereto recognizes and
acknowledges that a breach of any covenants or agreements contained in this
Agreement will cause Parent and Merger Sub to sustain damages for which they
would not have an adequate remedy at law for money damages, and therefore each
of the parties hereto agrees that in the event of any such breach Parent shall
be entitled to the remedy of specific performance of such covenants and
agreements and injunctive and other equitable relief in addition to any other
remedy to which they may be entitled, at law or in equity.

                            [SIGNATURE PAGE FOLLOWS]

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      The parties have caused this Agreement to be duly executed on the date
first above written.

                                     PARENT

                                     By: _______________________________________
                                     Name: _____________________________________
                                     Title: ____________________________________

                                     Address:  RITA Medical Systems, Inc.
                                     967 North Shoreline Blvd.
                                     Mountain View, CA  94043
                                     Attention:  Joseph DeVivo, President and
                                       Chief Executive Officer
                                     Facsimile No.:    (650) 967-1691

                                     COMPANY

                                     By: _______________________________________
                                     Name: _____________________________________
                                     Title: ____________________________________

                                     Address:  Horizon Medical Products, Inc.
                                     One Horizon Way
                                     Manchester, GA  91816
                                     Attention:  Robert Wenzel, President
                                     Facsimile No.:    (706) 846-5226

                       SIGNATURE PAGE TO VOTING AGREEMENT

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                                     HOLDER

                                     By: _______________________________________
                                     Name: _____________________________________
                                     Title: ____________________________________

                                     Holder's Address for Notice:

                                     ___________________________________________
                                     ___________________________________________
                                     ___________________________________________

Shares owned of record:                     Beneficially owned shares:
    Class of Shares      Number           Class of Shares          Number

                       SIGNATURE PAGE TO VOTING AGREEMENT

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                                    EXHIBIT A

                                IRREVOCABLE PROXY

                                TO VOTE STOCK OF

                         HORIZON MEDICAL PRODUCTS, INC.

                                       AND

                           RITA MEDICAL SYSTEMS, INC.

      The undersigned shareholder of Horizon Medical Products, Inc. a Georgia
corporation (the "Company"), hereby irrevocably (to the full extent permitted by
the Georgia Business Corporation Code) appoints the Chief Executive Officer and
Chief Financial Officer of RITA Medical Systems, Inc. a Delaware corporation
("Parent"), and each of them, as the sole and exclusive attorneys and proxies of
the undersigned, with full power of substitution and resubstitution, to vote and
exercise all voting and related rights (to the full extent that the undersigned
is entitled to do so) with respect to all of the shares of capital stock of the
Company and all of the shares of capital stock of Parent that now are or
hereafter may be owned of record or beneficially by the undersigned, and any and
all other shares or securities of the Company (collectively, the "Company
Shares") or Parent (collectively, the "Parent Shares" and together with the
Company Shares, the "Shares") issued or issuable in respect thereof on or after
the date hereof in accordance with the terms of this Proxy and that certain
Voting Agreement of even date herewith, by and among Parent, the Company and the
undersigned (the "Voting Agreement"). The shares of the capital stock of the
Company owned by the undersigned shareholder of the Company as of the date of
this Proxy are listed beneath the undersigned's signature on the final page of
this Proxy. Upon the undersigned's execution of this Proxy, any and all prior
proxies given by the undersigned with respect to any Shares are hereby revoked
and the undersigned agrees not to grant any subsequent proxies with respect to
the Shares until after the earlier to occur of (i) the Expiration Date (as
defined below) and (ii) the Effective Time (after which time the undersigned
agrees not to grant any proxy with respect to shares of the capital stock of
Parent in a manner inconsistent with this Proxy).

      This Proxy is coupled with an interest, is irrevocable (to the extent
permitted by the Georgia Business Corporation Code in the case of the capital
stock of the Company and, in the case of the capital stock of Parent, the
Delaware General Corporation Law), is granted pursuant to the Voting Agreement,
and is granted in consideration of Parent entering into that certain Agreement
and Plan of Merger, of even date herewith, by and among the Company, Parent and
Hornet Acquisition Corp., a Delaware corporation ("Merger Sub") and wholly-owned
subsidiary of Parent (the "Merger Agreement"). The Merger Agreement provides for
the merger of Merger Sub with and into the Company (the "Merger"). As used
herein, the term "Expiration Date" shall mean the earlier to occur of (i) the
date of termination of the Merger Agreement in accordance with the terms and
provisions thereof and (ii) the date on which the Company's Board of Directors
withdraws

<PAGE>

or modifies in a manner adverse to Parent or Merger Sub the Company
Recommendation (as defined in the Merger Agreement) in accordance with the
requirements of the second sentence of Section 4.3(e) of the Merger Agreement.

      The attorneys and proxies named above, and each of them, are hereby
further authorized and empowered by the undersigned, at any time prior to the
earlier to occur of (i) the Effective Time and (ii) Expiration Date, to act as
the undersigned's attorney and proxy to vote the Shares, and to exercise all
voting and other rights of the undersigned with respect to the Shares
(including, without limitation, the power to execute and deliver written
consents pursuant to the Georgia Business Corporation Code), at every annual,
special or adjourned meeting of the shareholders of the Company and in every
written consent in lieu of such meeting (i) in favor of approval of the Merger
and the Merger Agreement and (ii) against any proposal for any recapitalization,
merger, sale of assets or other business combination (other than the Merger)
between the Company and any person or entity other than Parent or any other
action or agreement that could reasonably be expected to result in a breach of
any covenant, representation or warranty or any other obligation or agreement of
the Company under the Merger Agreement or the undersigned under the Voting
Agreement or which could reasonably be expected to result in any of the
conditions to the Company's obligations under the Merger Agreement not being
fulfilled.

      The attorneys and proxies named above, and each of them, are hereby
authorized and empowered by the undersigned, at any time prior to the earlier to
occur (i) the Expiration Date and (ii) the date following the date of the 2005
annual meeting of stockholders of Parent, including any adjournment or
postponement thereof, to act as the undersigned's attorney and proxy to vote all
Parent Shares owned beneficially or of record by the undersigned as of the
record date for each annual meeting of Parent stockholders, and to exercise all
voting and other rights of the undersigned with respect to such shares
(including, without limitation, the power to execute and deliver written
consents pursuant to the Delaware General Corporation Law), at every annual
meeting of the stockholders of Parent, including any adjournment or postponement
thereof, in favor of the election of nominees to the Board of Directors of
Parent recommended for election by the Board of Directors of Parent.

      Any obligation of the undersigned hereunder shall be binding upon the
successors and assigns of the undersigned.

      This Proxy is irrevocable (with respect to the shares of capital stock of
the Company, to the extent provided in the Georgia Business Corporation Code
and, with respect to the shares of capital stock of Parent, to the extent
provided in the Delaware General Corporation Law).

                            [SIGNATURE PAGE FOLLOWS]

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Dated: May __, 2004

_____________________________________
(Signature of Holder)

_____________________________________
(Print Name of Holder)

_____________________________________
(Title of Signatory if Holder is an Entity)

Shares owned of record:                     Beneficially owned shares:
    Class of Shares        Number           Class of Shares          Number

                       SIGNATURE PAGE TO IRREVOCABLE PROXY<PAGE>

                                                                    EXHIBIT 10.2

                                LOCK-UP AGREEMENT

      THIS LOCK-UP AGREEMENT (this "Agreement") is made and entered into as of
May 12, 2004, by and among RITA Medical Systems, Inc., a Delaware corporation
("Parent"), Horizon Medical Products, Inc., a Georgia corporation (the
"Company"), and the undersigned shareholder of the Company ("Holder").
Capitalized terms used but not otherwise defined herein shall have the meanings
ascribed to them in the Merger Agreement (as defined below).

                                   BACKGROUND

      A. Parent, the Company and Hornet Acquisition Corp., a Delaware
corporation and wholly owned subsidiary of Parent ("Merger Sub"), have entered
into an Agreement and Plan of Merger, dated as of the date hereof (the "Merger
Agreement"), which provides for the merger of the Merger Sub with and into the
Company (the "Merger"), pursuant to which the Company shall become a
wholly-owned subsidiary of Parent.

      B. Holder has been advised that Holder may be deemed to be an "affiliate"
of Parent after the consummation of the Merger as the term "affiliate" is
defined in Rule 144 of the Rules and Regulations (the "Rules and Regulations")
of the Securities and Exchange Commission (the "Commission"), although nothing
contained herein shall be construed as an admission by Holder that Holder will
in fact be an "affiliate" of Parent after the consummation of the Merger.

      C. As a condition and inducement to the willingness of Parent, Merger Sub
and the Company to enter into the Merger Agreement, Holder has agreed to enter
into this Agreement.

      NOW, THEREFORE, intending to be legally bound, the parties hereto agree as
follows:

      1. Acknowledgments by Holder. Holder has carefully read this Agreement and
the Merger Agreement and has had the opportunity to discuss the requirements of
this Agreement with Holder's professional advisors, who Holder believes are
qualified to advise Holder with regard to such matters.

      2. Affiliate Status; Lock-up.

            (a) Affiliate Status. Holder has been advised that (i) the issuance
of Parent Common Stock to Holder Company Shareholders in connection with the
Merger will be registered on a registration statement on Form S-4 promulgated
under the Securities Act of 1933, as amended (the "1933 Act") and that the
resale by Holder of shares of Parent Common Stock issued to the undersigned in
the Merger will be registered under the 1933 Act on a post-effective amendment
to such registration statement on Form S-3 (the "Resale Registration
Statement"), (ii) the resale of such shares by Holder may be subject to
restrictions set forth in Rule 144 and Rule 145 of the Rules and Regulations,
and (iii) Holder may be deemed to be an affiliate of Parent after the
consummation of the Merger.

<PAGE>

            (b) Lock-up. Holder agrees, during the 12-month period beginning on
the date of the consummation of the Merger, not to offer, contract to sell or
otherwise sell, dispose of, loan, pledge, grant any rights with respect to, make
any short sale of, grant any option for the purchase of, or enter into any
hedging or similar transaction with the same economic effect as a sale (each, a
"Disposition") of any shares of Parent Common Stock, except to the extent that:
(A)(i) such Disposition is made in conformity with the requirements of Rule
145(d) promulgated under the 1933 Act, to the extent such Rule may be applicable
to such Disposition, (ii) such Disposition is made pursuant to an effective
registration statement under the 1933 Act or an appropriate exemption from
registration or (iii) Holder delivers to Parent a written opinion of counsel,
reasonably acceptable to Parent in form and substance, that such Disposition is
otherwise exempt from registration under the 1933 Act; and (B) the number of
shares of Parent Common Stock subject to Dispositions made by Holder during the
three month-period ending on the date of any such Disposition (and including the
shares of Parent Common Stock subject to such Disposition) does not exceed 200%
of the number of shares of Parent Common Stock Holder would be entitled to sell
in accordance with the volume limitations set forth in Rule 144(e)(1) of the
Rules and Regulations if all shares of Parent Common Stock subject to
Dispositions made by Holder during such three-month period were subject to such
volume limitations (regardless of whether the resale thereof has been registered
under the 1933 Act). Notwithstanding anything to the contrary herein, this
Agreement shall not prohibit a transfer of any shares of Parent Common Stock by
Holder, if Holder is a partnership or limited liability company, to one or more
partners or members of Holder or to an affiliated Person under common control
with Holder; provided, however, that unless such transfer is effected in
accordance with Section 2(b)(B) above, such transfer shall be permitted only if,
as a precondition to such transfer, the transferee agrees in writing to be bound
by all of the terms of this Section 2(b).

            (c) Holder understands that there will be placed on the certificates
for the Parent Common Stock issued to Holder, or any substitutions therefor, a
legend stating in substance:

      "THE SHARES REPRESENTED BY THIS CERTIFICATE ARE HELD BY AN "AFFILIATE" OF
      RITA MEDICAL SYSTEMS, INC. AND MAY ONLY BE TRANSFERRED IN ACCORDANCE WITH
      RULE 144 UNDER THE SECURITIES ACT OF 1933, AND WERE ISSUED IN A
      TRANSACTION TO WHICH RULE 145 PROMULGATED UNDER THE SECURITIES ACT OF 1933
      APPLIES. THE SHARES REPRESENTED BY THIS CERTIFICATE MAY ONLY BE
      TRANSFERRED IN ACCORDANCE WITH THE TERMS OF AN AGREEMENT DATED MAY __,
      2004 BETWEEN THE REGISTERED HOLDER HEREOF, RITA MEDICAL SYSTEMS, INC. AND
      HORIZON MEDICAL PRODUCTS, INC., A COPY OF WHICH AGREEMENT IS ON FILE AT
      THE PRINCIPAL OFFICES OF RITA MEDICAL SYSTEMS, INC."

It is understood and agreed that the legend contemplated in this Section 2(c)
shall be removed by delivery of a substitute certificate without such legend if
Holder shall have delivered to Parent a copy of a letter from the staff of the
Securities and Exchange Commission, or a written opinion of counsel reasonably
acceptable to Parent, to the effect that such legend is not required for
purposes of the 1933 Act; provided, however, it is further understood and agreed
that if one year has passed since Holder's acquisition of Parent Common Stock as
a result of the Merger (as

                                      -2-
<PAGE>

determined in accordance with paragraph (d) of Rule 144 under the 1933 Act) and
Holder is not an "affiliate" of Parent, Holder may request of Parent in writing
that the legend contemplated in this Section 2(c) be removed by delivery of a
substitute certificate without such legend and Parent thereafter will cause such
substitute certificate to be issued to Holder, without the delivery of such a
letter or written opinion.

            (d) As soon as practicable following the execution of the Merger
Agreement, Parent shall prepare (together with the Company) and file with the
Commission, a joint registration and proxy statement consisting of the Company
Proxy Statement, the Parent Proxy Statement and the Registration Statement (as
such terms are defined in the Merger Agreement) for the offer and sale of Parent
Common Stock pursuant to the Merger, included in which shall be the Company
Proxy Statement and the Parent Proxy Statement which shall constitute a
prospectus. Parent shall use commercially reasonable efforts to have the
Registration Statement declared effective under the 1933 Act as promptly as
practicable after its filing. Parent agrees to use its commercially reasonable
efforts to: (i) file the Resale Registration Statement within ten (10) days
subsequent to the Effective Time; (ii) cause the Resale Registration Statement
to be declared effective under the Securities Act as promptly as practicable
after its filing; and (iii) maintain the effectiveness of the Resale
Registration Statement for a period of time ending on the earlier of (A) the
date on which all shares of Parent Common Stock issued in connection with the
Merger to Holder have been sold and (B) the date on which all shares of Parent
Common Stock held by Holder issued to Holder in connection with the Merger, in
the opinion of counsel for Parent, are eligible for sale pursuant to Rule 144
under the 1933 Act and could be sold in any three-month period in accordance
with the volume limitations contained in Rule 144(e)(1) under the 1933 Act.

      3. Termination.

      This Agreement shall terminate and shall be of no further force and effect
in the event of the termination of the Merger Agreement at any time prior to the
Effective Time.

      4. Miscellaneous.

            (a) Waiver; Severability. No waiver by any party hereto of any
condition or of any breach of any provision of this Agreement shall be effective
unless in writing and signed by each party hereto. In the event that any
provision of this Agreement, or the application of any such provision to any
person, entity or set of circumstances, shall be determined to be invalid,
unlawful, void or unenforceable to any extent, the remainder of this Agreement,
and the application of such provision to persons, entities or circumstances
other than those as to which it is determined to be invalid, unlawful, void or
unenforceable, shall not be impaired or otherwise affected and shall continue to
be valid and enforceable to the fullest extent permitted by law.

            (b) Binding Effect and Assignment. This Agreement and all of the
provisions hereof shall be binding upon and inure to the benefit of the parties
hereto and their respective successors and permitted assigns, but, except as
otherwise specifically provided herein, neither

                                      -3-
<PAGE>

this Agreement nor any of the rights, interests or obligations of the parties
hereto may be assigned by either of the parties without prior written consent of
the other party hereto.

            (c) Amendments and Modification. This Agreement may not be modified,
amended, altered or supplemented except upon the execution and delivery of a
written agreement executed by the parties hereto.

            (d) Governing Law. This Agreement shall be governed by and
construed, interpreted and enforced in accordance with the internal laws of the
State of Delaware without giving effect to any choice or conflict of law
provision or rule (whether of the State of Delaware or any other jurisdiction)
that would cause the application of the laws of any jurisdiction other than the
State of Delaware.

            (e) Entire Agreement. This Agreement sets forth the entire
understanding of Holder, Parent and the Company relating to the subject matter
hereof and supersedes all prior agreements and understandings among Holder,
Parent and the Company relating to the subject matter hereof.

            (f) Attorneys' Fees. In the event of any legal actions or proceeding
to enforce or interpret the provisions hereof, the prevailing party shall be
entitled to reasonable attorneys' fees, whether or not the proceeding results in
a final judgment.

            (g) Further Assurances. Holder shall execute and/or cause to be
delivered to Parent and the Company such instruments and other documents and
shall take such other actions as Parent may reasonably request to effectuate the
intent and purposes of this Agreement.

            (h) Survival. The representations, warranties, covenants and other
provisions contained in this Agreement shall survive the consummation of the
Merger.

            (i) Notices. All notices and other communications pursuant to this
Agreement shall be in writing and deemed to be sufficient if contained in a
written instrument and shall be deemed given if delivered personally, by
facsimile, sent by nationally-recognized overnight courier or mailed by
registered or certified mail (return receipt requested), postage prepaid, to the
parties at the following address (or at such other address for a party as shall
be specified by like notice):

                                    If to Parent:

                                    RITA Medical Systems, Inc.
                                    967 North Shoreline Blvd.
                                    Mountain View, CA  94043

                                    Attention:  Joseph DeVivo, President and
                                      Chief Executive Officer
                                    Facsimile No.: (650) 967-1691

                                    with a copy to:

                                      -4-
<PAGE>

                                    Heller Ehrman White & McAuliffe LLP
                                    2775 Sand Hill Road
                                    Menlo Park, California 94025
                                    Attention:     Mark Weeks
                                                   Steve Tonsfeldt
                                    Facsimile No.: (650) 233-8386

                                    If to the Company:

                                    Horizon Medical Products, Inc.
                                    One Horizon Way
                                    Manchester, GA 91816
                                    Attention: Robert Wenzel, President
                                    Facsimile No.: (706) 846-5226

                                    with a copy to:
                                    King & Spalding LLP
                                    191 Peachtree Street
                                    Atlanta, Georgia 30303
                                    Attention: Jon R. Harris, Jr.
                                    Facsimile No.: (404) 572-5136

            If to Holder:       To the address for notice set forth on the
                                signature page hereof.

            (j) Counterparts. This Agreement shall be executed in one or more
counterparts, each of which shall be deemed an original, and all of which
together shall constitute one and the same instrument.

                            [SIGNATURE PAGE FOLLOWS]

                                      -5-
<PAGE>

      IN WITNESS WHEREOF, the parties have caused this Lock-Up Agreement to be
duly executed on the day and year first above written.

RITA MEDICAL SYSTEMS, INC.              HORIZON MEDICAL PRODUCTS, INC.

By: _________________________________   By: ____________________________________

Name: _______________________________   Name: __________________________________

Title: ______________________________   Title: _________________________________

HOLDER

By: _________________________________

Name: _______________________________

Title: ______________________________

Holder's address for notices:

_____________________________________
_____________________________________
_____________________________________

                       SIGNATURE PAGE TO LOCK-UP AGREEMENT

                                      -6-

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