AMENDED AND RESTATED EMPLOYMENT AGREEMENT

         This Employment  Agreement is made as of the 14 day of December,  1999,
by and between Symbollon Corporation,  a Delaware corporation with its principal
place of business at 37 Loring Drive, Framingham, MA 01702 (the "Company"),  and
Jack H. Kessler, residing at 56 Presidential Drive, Southborough,  MA 01772 (the
"Employee").

         In  consideration  of the mutual promises  contained in this Agreement,
the parties agree as follows:

         1. Titles and Responsibilities.  The Company employs the Employee,  and
the Employee accepts employment, as Chief Executive Officer and Chief Scientific
Officer  of  the  Company.  The  Employee  shall  be  directly  responsible  for
management of all business operations and setting of overall corporate strategy.
Subject to the general  direction  and control of the Board of  Directors of the
Company  (the  "Board"),  the  Employee  agrees to devote his full time and best
efforts to his duties and responsibilities for the Company,  subject only to the
provisions of Section 7 of this Agreement. The Employee shall report directly to
the Board.

         2. Term. The term of this  Agreement  shall be deemed to have commenced
as of the date  hereof  and,  subject  to the  provisions  of Section 12 of this
Agreement, shall continue in full force and effect until December 31, 2005.

         3. Base Salary.  During the term of this Agreement,  the Employee shall
be entitled to receive base salary at the rate of $175,000 per year, payable not
less than monthly in arrears,  commencing  January,  2000. The  Employee's  base
salary  (at  the  rate  then  in  effect)  shall  be  increased  each  year by a
cost-of-living  factor  determined by reference to the Consumers Price Index for
All Urban Consumers applicable to Boston, Massachusetts, published by the Bureau
of Labor Statistics of the U.S. Department of Labor (the "Index"). The amount of
such increase  shall be effective in January of each year,  commencing  January,
2001,  and  shall be equal to the  percentage  increase  in the  Index  from the
previous  January.  The Company may, but shall not be obligated to, increase the
Employee's base salary in any year in an amount in excess of the  cost-of-living
factor provided above.

         4.  Bonuses.

         (a).  Annual.  In addition to the base salary  described  in Section 3,
during the term of this Agreement, the Employee may be entitled in each calendar
year to receive a cash bonus,  stock options and/or such other bonuses,  in such
amounts  and on such  terms as the Board or the  Compensation  Committee  of the
Board  (the  "Compensation  Committee")  may  determine.  In  the  event  of the
termination  of the  employment  of the  Employee  for (i) any reason other than
Cause  or (ii) by  reason  of  Constructive  Discharge,  the  Employee  shall be
entitled to receive an amount equal to the bonus which would otherwise have been
payable to the Employee under any established  Company  incentive plans, if any,
in effect at the time in  respect  of the year  during  which  such  termination
occurs, pro rated for the portion of the year in which such termination occurs.


<PAGE>

         (b).     Signing.  As an  incentive  to execute this  Agreement,  the
Employee  shall be granted as of the date hereof options to purchase Class A
Common Stock as detailed on Exhibit A hereto.

         5. Employee Benefits.  The Employee shall have the right to participate
in all benefit plans and programs  generally made available to executives of the
Company,  including  without  limitation  health,  dental,  life, and disability
insurance, vacation programs, retirement plans, employee stock plans or benefits
and profit sharing plans.

         6. Reimbursement of Expenses.  The Company shall reimburse the Employee
for all reasonable and necessary  expenses incurred by him in the performance of
his duties hereunder,  following his appropriate substantiation thereof, in each
case in accordance with the Company's policies as in effect from time to time.

         7. Outside  Consulting.  With prior  notification  to the  Compensation
Committee,  the Employee may provide consulting  services to third parties.  The
Employee may serve as a consultant in any field which does not directly  compete
with the Company,  including without  limitation,  medical diagnostic  products,
provided,  that in no event shall such proposed  consulting  interfere  with the
operations of the Company or the performance of the Employee's duties under this
Agreement more  particularly  described in Section 1 hereof. If the Compensation
Committee  shall  determine  that  any  consulting  activity  engaged  in by the
Employee is not permitted  hereunder,  the Compensation  Committee shall provide
the Employee a written statement setting forth the basis for its  determination.
The  Employee  agrees  that in no event  will he devote  more than four days per
month in the aggregate in his capacity as a consultant to third parties.

         The  Company  acknowledges  that the  Employee  is a  principal  of and
participant  in K&R  Associates,  that K&R  Associates  owns  rights to  certain
elements  of the  Company's  technology  as it  relates to the  disinfection  of
contact lenses, and that the Employee is currently providing consulting services
to K&R  Associates  and  Ciba-Vision  Corporation  in the field of contact  lens
disinfection.  The  Company  hereby  consents to the  Employee's  aforementioned
consulting activities.

         8.  Severance and Other Arrangements.

         (a)      Generally.  In the event of the  termination  of the
employment  of the  Employee by the Company without Cause, or by the Employee as
the result of a Constructive Discharge, the Company shall:

                  (i).  Continue to pay the  Employee,  in  accordance  with the
Company's  normal  payroll  practices  and  policies in effect from time to time
(including any required withholding), his base salary at the monthly base salary
rate in effect for such Employee  immediately  prior to the  termination  of his
employment)  for a period of eighteen (18) months  following the  termination of
the Employee's employment.

                  (ii).  Provide the  Employee  with  health,  dental,  life and
disability  insurance  substantially  similar  to that  which the  Employee  was
receiving  immediately  prior to the  termination  of his  employment  until the
earlier of: (x) the date which is eighteen (18) months following the termination
of the Employee's  employment;  or (y) the date the Employment  begins receiving
substantially  similar  insurance  from a  subsequent  employer.  The end of the
period  during which  severance  is paid,  rather than the  termination  date of
employment,  will be deemed to be a  "qualifying  event" which would entitle the

<PAGE>

Employee  to  acquire at his own  expense  during the  minimum  election  period
permitted by the Consolidated Omnibus Budget  Reconciliation Act (commonly known
as "COBRA") or such law as may then be in effect  continuation of coverage under
the Company's health and benefit plans.

                  (iii). Provide that the Employee shall have three (3) years to
exercise any then-exercisable,  unexpired installments of any stock options held
by the Employee on the Employee's last date of employment or if later,  the date
when the Employee ceases to be a member of the Board.

         (b)  Disability.  In the event of any illness  (mental or  physical) or
accident   which  renders  the  Employee   unable  to  perform  his  duties  and
responsibilities,  the  Company  shall,  during  the  first 3 months of any such
illness  or  after  such  accident,  as the  case  may be,  continue  to pay the
Employee's  base salary  hereunder;  and  thereafter,  during any such period in
excess of 3 months the Company shall  supplement any  disability  benefits which
the Employee is entitled to receive under the Company's disability plans then in
effect,  for a period of up to 9  additional  months,  in an amount  such  that,
together  with any amounts the Employee is entitled to receive under such plans,
the Employee  shall receive an aggregate  amount equal to his base salary during
such period.

         (c).     Change of Control.  Upon a Change of Control,  all stock
options held by the Employee  shall vest and become immediately exercisable
in full.

         9.  Non-competition.  During the term of this  Agreement and thereafter
the Employee will not directly or  indirectly,  participant in any business that
utilizes the Company's proprietary information, know-how or trade secrets in any
field of activity, including specifically those fields that are competitive with
the  business  of  the  Company,  nor  will  the  Employee  interfere  with  the
contractual  relations  between  the  Company  and  any  of its  employees.  The
provisions  of this Section  shall not  prohibit  the  ownership of stock in any
entity whose stock is publicly traded or 5% or less of the outstanding  stock of
any entity whose stock is not publicly traded.

         The Company  acknowledges  that  certain  rights to  commercialize  the
Company's   enzyme-based   iodine  technology  in  the  field  of  contact  lens
disinfection are owned by K&R Associates.

         10.  Ownership of  Developments.  The Employee  agrees that any work or
research,  or the  result  thereof  including  without  limitation,  inventions,
processes,  formula, data, information,  programs, systems, software or know-how
(hereinafter   collectively   "Proprietary   Information")  made,  conceived  or
developed by Employee,  alone or in connection  with others,  prior to or during
the term of his employment  under this  Agreement,  whether during or out of the
usual hours of  employment,  which are  related to the  business,  research  and
development  work  within  the  Company's  Field of  Operation  are the sole and
exclusive property of the Company. The Employee agrees that he will fully assign
the  foregoing  to  Company.   The  Employee  further  agrees  to  disclose  all
Proprietary Information completely and in writing to the Board. To the extent of
the Employee's interest therein,  all papers and records of every kind, relating
to Proprietary  Information  included within the terms of this Agreement,  which
shall at any time come into the possession of the Employee shall be the sole and
exclusive  property of the Company and shall be  surrendered to the Company upon
termination  of the  Employee's  employment by the Company or upon the Company's
request at any time either during or after the termination of such employment.


<PAGE>

         11.  Confidential  Information.  Employee covenants and agrees with the
Company that Employee  will not during or after the term of employment  disclose
to anyone (except to the extent reasonably necessary for Employee to perform his
duties hereunder) any Proprietary Information or other confidential  information
concerning the business or affairs of the Company or of any of its affiliates or
subsidiaries  or any of their  customers which Employee may have acquired in the
course of or as incident to  Employee's  employment  or prior  dealings with the
Company or with any of its affiliates,  including without limitation,  customers
lists,  or business trade secrets of, or methods or techniques  used by Employee
or any  of  its  affiliates  in or  about  their  respective  business.  Nothing
contained  in this  paragraph  shall impair or restrict the right of Employee to
use or disclose any information already in the public domain.

         12.  Termination.  Notwithstanding  the provisions of Section 2 of this
Agreement,  the Company shall have the right to terminate the  employment of the
Employee for Cause or as a result of his death or Permanent Disability,  and the
Employee  shall have the right to terminate  his  employment  as the result of a
Constructive  Discharge,  in each case  without  violation  of the terms of this
Agreement.

         In no event shall the Company  terminate this Agreement  without Cause,
unless  the  Employee  shall  have been  granted a prior  meeting  with,  and an
opportunity  to be heard by, the Board,  and a  majority  of the  members of the
Board  shall have  determined  that the  Employee  has (i) failed to fulfill his
duties to the  Company  in a  satisfactory  manner or (ii)  engaged  in  conduct
detrimental to the Company.

         13.  Certain  Definitions.  For purposes of this  Agreement,  the
following  terms shall have the meanings indicated:

                  "Cause"  means (i) the  deliberate  dishonesty of the Employee
with  respect to the  Company  or any  subsidiary  or  affiliate  thereof;  (ii)
conviction of the Employee of a felony  punishable by imprisonment for more than
one year or a fine of $100,000 or more; or (iii) the willful failure of Employee
to perform the material  lawful duties  assigned to him under this  Agreement as
determined by the Board, which failure the Employee shall not have substantially
remedied  within  30 days  after  receiving  written  notice  from  the  Company
describing such failure in reasonable detail.



<PAGE>


                  "Change of  Control"  means (i) the sale,  lease,  transfer or
other  disposition by the Company of all or substantially all of its assets in a
single  transaction  or a series of  related  transactions;  (ii) the  merger or
consolidation  of the Company with another entity in which the  stockholders  of
the Company immediately prior to such merger or consolidation hold less than 50%
of the  outstanding  voting  stock of the  surviving  or  resulting  corporation
immediately  following  such  transaction;  or (iii) the sale or exchange (to or
with any person or entity  other than the  Company) by the  stockholders  of the
Company of more than 50% of the  outstanding  voting  stock of the  Company in a
single transaction or series of related transactions.

                  "Company's  Field of Operation"  means all therapeutic  and/or
anti-microbial products, including without limitation iodine-based products, and
any additional products or services developed, marketed,  distributed,  planned,
sold or  otherwise  provided by the Company from time to time prior to or during
the term of this Agreement.

                  "Constructive  Discharge"  means the termination of employment
by the Employee on the grounds that (a) there has been a  significant  reduction
in the nature or scope of the Employee's responsibilities,  authorities, powers,
functions  or  duties,  (b) there has been a  material  change in the  Company's
policies or management  which was intended other than in good faith to and which
has  resulted in the  inability of the  employee to exercise  substantially  the
responsibilities,  authorities,  powers,  functions  or duties  exercised by him
immediately  prior to such  change,  (c) there has been a decrease  in the total
annual  compensation  payable by the  Company to the  Employee,  other than as a
result of a material decrease in compensation payable to the Employee and to all
other  employees  of similar rank and stature of the Company on the basis of the
financial performance of the Company, provided,  however, that nothing contained
herein  shall be  construed  as giving the  Company  the right to  decrease  the
Employee's  base  salary  specified  in  Section 3 hereof,  (d) there has been a
Change of Control  within the past twelve (12) months,  or (e) the relocation of
the  Company's  business  to a site more than  twenty-five  (25)  miles from the
Employee's residence.

                  "Permanent  Disability"  means illness (mental or physical) or
accident   which  renders  the  Employee   unable  to  perform  his  duties  and
responsibilities  for a period of six  consecutive  months or six  months in any
twelve-month  period,  and which is confirmed to the Board as  continuing at the
end of  such  period  by  expert  medical  opinion.  Nothing  contained  in this
Agreement shall affect the right of the Employee to receive long-term disability
benefits under any long-term disability insurance plan(s) of the Company then in
effect.

         14.  Miscellaneous.

         (a)  Notices.  Any notice  hereunder  shall be  effective  if delivered
personally,  by registered  or certified  mail,  return  receipt  requested,  by
overnight  or special  courier  with a signed  receipt,  or by  facsimile  where
confirmation  of receipt  may be  verified,  at the  addresses  set forth in the
preamble to this Agreement or to any other properly noticed address given by the
parties to each other.



<PAGE>


         (b)      Governing  Law. This  Agreement  shall be construed  and
governed by the law of the  Commonwealth of Massachusetts.

         (c)      Amendments.  This Agreement may not be modified or amended
orally.  All  amendments  shall be in writing and signed by the Company and
Employee.

         (d) Assignments. This Agreement may not be assigned in whole or in part
by the  Employee.  This  Agreement  may be assigned by the Company to any entity
acquiring or succeeding to control of ownership of the Company or  substantially
all of the assets of the Company. This Agreement shall be binding upon and inure
to the benefit of the parties and to their permitted successors and assigns.

         (e)      Entire  Agreement.  This  Agreement  constitutes  the entire
understanding  of the parties  with respect to its  subject  matter and
supersedes  any other  agreements  between the  parties  with  respect to such
subject matter.

         (f) Enforceability. If any portion or provision of this Agreement shall
to any extent be  declared  illegal  or  unenforceable  by a court of  competent
jurisdiction,  then the remainder of this Agreement,  or the application of such
portion  or  provision  in  circumstances  other than those as to which it is so
declared  illegal or  unenforceable,  shall not be  affected  thereby,  and each
portion and provisions of this Agreement  shall be valid and  enforceable to the
fullest extent permitted by law.

         (g) Waiver. No waiver of any provision hereof shall be effective unless
made in writing  and signed by the  waiving  party.  The failure of any party to
require the  performance  of any term or  obligation of this  Agreement,  or the
waiver  by any party of any  breach of this  Agreement,  shall not  prevent  any
subsequent  enforcement  of such term or obligation or be deemed a waiver of any
subsequent breach.

         (h)  Arbitration.  Any  controversy  or claim  which  arises  out of or
relating to this Agreement,  or the breach thereof (other than  controversies or
claims with regard to Sections 9, 10 or 11 of this Agreement),  shall be settled
by  arbitration  in  accordance  with  the  Rules  of the  American  Arbitration
Association then in effect. The controversy or claim shall be submitted to three
arbitrators,  one of whom shall be chosen by the Employee,  one of whom shall be
chosen by the  Company,  and one of whom shall be chosen by the two so selected.
The party desiring  arbitration  shall give written notice to the other party of
its desire to arbitrate the particular matter in question, naming the arbitrator
selected  by it. If the other  party shall fail within a period of 15 days after
such  notice  shall have been given to reply in  writing  naming the  arbitrator
chosen as above  provided,  or if the two  arbitrators  selected  by the parties
shall  fail  within  15 days  after  their  selection  to agree  upon the  third
arbitrator,  then either party may apply to the American Arbitration Association
for the appointment of an arbitrator to fill the place so remaining vacant.  The
decision  of any two of the  arbitrators  shall be final  and  binding  upon the
parties  hereto.  Judgement  upon the award rendered by the  arbitrators  may be
entered in any court having jurisdiction thereof.

         The proceedings shall be held in Boston, Massachusetts. The arbitrators
shall have no power to award punitive or exemplary  damages or to ignore or vary
the  terms of this  Agreement,  and  shall be  bound to apply  controlling  law.
Arbitration  shall  be  binding  and  the  remedy  for  the  settlement  of  the
controversy  or claims  (except as set forth in the preceding  paragraph of this
Section).


<PAGE>

         (i) Certain Remedies.  The restrictions contained in Sections 9, 10 and
11 of this  Agreement  are  necessary  for the  protection  of the  business and
goodwill of the Company and are  considered by the Employee to be reasonable for
such  purpose.  Without  limiting  the remedies  available  to the Company,  the
Employee  acknowledges that a breach of any of the covenants contained in any of
such Sections 9, 10 and 11 would result in irreparable injury to the Company for
which there might be no adequate remedy at law, and that, in the event of such a
breach or threat  thereof,  the Company  shall be entitled to obtain a temporary
restraining  order  and/or  such other  equitable  relief as may be  required to
enforce  specifically  any of the  covenants of such  Sections 9, 10 and 11. The
provisions of such Sections 9, 10 and 11 shall survive the  termination  of this
Agreement and shall continue thereafter indefinitely in full force and effect in
accordance with their respective terms.

         IN WITNESS  WHEREOF,  the  parties  have caused  this  Agreement  to be
executed as of the date and year first above written.

                                            SYMBOLLON CORPORATION



                                            By: /s/ Paul C. Desjourdy
                                                -------------------------------
                                                Paul C. Desjourdy
                                                President

                                                /s/ Jack H. Kessler
                                                -------------------------------
                                                Jack H. Kessler



<PAGE>




                                    Exhibit A

                                  Option Grant


     Number of Shares      Exercise Price                   Vesting Date

         60,000            150% of Fair Market Value*     First Anniversary

         60,000            200% of Fair Market Value*     Second Anniversary

         60,000            250% of Fair Market Value*     Third Anniversary
         ------

        180,000


* Fair  Market  Value of the  Class A Common  Stock,  as  determined  under  the
Company's 1993 Employee Stock Option Plan, as amended, on the date of grant.