Exhibit 10.20

                                      DEBENTURE
                                      ---------


          STAMPED TO COVER $15,000,000 UNITED STATES CURRENCY

          THIS DEBENTURE IS MADE THE 12TH DAY OF NOVEMBER, 1996.

                  BETWEEN

                  Murex Diagnostics  Corporation, a company incorporated and
                  registered  in Anguilla  and continued  in Barbados  under
                  the provisions  of the Companies  Act Cap.  308 as Company
                  No. 11016  and  Murex Diagnostics  International, Inc.,  a
                  company incorporated and  registered in Barbados under the
                  provisions  of  the  Companies  Act  Cap.  308 as  Company
                  No. 11019 (hereinafter  together called  the "Company") of
                  the FIRST PART, and

                  Bank  of America, FSB,  whose principal  office is located
                  at 1230  Peachtree Street,  Suite 3600, Atlanta,  Georgia,
                  USA  30309  (hereinafter  called  the  "Chargee")  of  the
                  SECOND PART


                  NOW THIS DEBENTURE WITNESSETH  that for good  and valuable
                  consideration,  the receipt  and sufficiency of  which the
                  Company  hereby  jointly  and severally  acknowledges, the
                  Company has  agreed to  execute and  issue this  Debenture
                  unto the Chargee  for the purpose of securing the  payment
                  to the Chargee of the Indebtedness as hereinafter  defined
                  and  of all  such sums  of  money now  owing or  that  may
                  hereafter  become  due  and  owing  to  the  Chargee,  the
                  Lenders  or the  Issuing Bank  (as  defined in  the Credit
                  Agreement) under the Credit Agreement (as defined below).


                  1.1  In this Debenture:

                       "Act" means  the Companies Act Cap.  308 of the  Laws
                       of  Barbados (or  any statutory  modification or  re-
                       enactment of that Act for the time being in force);

                       "Assets"  means   the  joint  and  several  property,
                       undertaking and  assets of  the Company  expressed to
                       be  charged to  the Chargee  now or  hereafter  under
                       Clause 2;

                       "Event of Default"  has the meaning set forth in  the
                       Credit  Agreement   (as  hereinafter  described,  the
                       relevant  clauses of which are incorporated herein by
                       reference thereto).

                       "Indebtedness" means all amounts  due under a certain
                       Credit  Agreement  dated  ___ November,  1996 between
                       Murex Diagnostics  Corporation and  Murex Diagnostics
                       International,  Inc.,  certain  affiliates  of  Murex
                       Diagnostics   Corporation   and   Murex   Diagnostics
                       International, Inc.,  the Lenders,  the Issuing Banks
                       and  the  Chargee  (including any  document amending,
                       supplementing, novating  or replacing  the same,  the
                       "Credit  Agreement")  together  with interest  to the
                       date  of repayment  chargeable  and payable  in  such
                       manner as has been  specifically agreed and any other
                       costs,   charges  and  legal   expenses  (on  a  full
                       indemnity basis)  charged or incurred  by the Chargee
                       in  connection   with  said   Credit  Agreement   and
                       including those  arising from  the Chargee perfecting
                       or enforcing or attempting to  enforce this Debenture
                       or  any other  security (and  its rights  thereunder)
                       held by the Chargee from  time to time  and including
                       all   Obligations   (as   defined   in   the   Credit
                       Agreement);

                       "Receiver" means one or more persons appointed to  be
                       a  receiver,  receivers,  and/or  a  receiver/manager
                       pursuant to Clause 7.2 of this Debenture.

                       "Subsidiary"  has the meaning ascribed thereto in the
                       Companies Act Cap. 308 of the Laws of Barbados.

                  1.2  Clause headings are for ease of reference only.   All
                       capitalized  terms used but not  defined herein shall
                       have the  meanings ascribed to such terms in the said
                       Credit Agreement.

          2.      CHARGE
                  ------

                  2.1  The Company  hereby jointly  and severally  covenants
                       on demand  to pay  or discharge  the Indebtedness  to
                       the  Chargee.    As  security  for  the  payment  and
                       discharge  of the Indebtedness, the Company, as legal
                       and beneficial  owner, hereby  jointly and  severally
                       charges to the Chargee:

                       2.1.1     by  way   of  floating   charge,  all   the
                                 goodwill and  uncalled capital for the time
                                 being of the Company;

                       2.1.2     by way  of floating  charge, all rights  of
                                 Murex  Diagnostics Corporation  under  that
                                 certain  License  Agreement,  dated May  3,
                                 1994,     between     Murex     Diagnostics
                                 Corporation  and Abbott  Laboratories,  and
                                 all choses in action  and claims now and in
                                 the future belonging  to Murex  Diagnostics
                                 Corporation;

                       2.1.3     by  way  of floating  charge, all  stock in
                                 trade and  inventory in  all of its  forms,
                                 wherever   located,   now   or    hereafter
                                 existing (including,  but  not limited  to,
                                 (i)   all  goods,   merchandise  and  other
                                 personal property  owned and held for sale,
                                 and (ii) all  raw materials, work or  goods
                                 in  process,  finished  goods  thereof, and
                                 materials and  supplies which contribute to
                                 the  finished  products  of Company  in the
                                 ordinary  course  of  business  and   (iii)
                                 goods which  are returned to or repossessed
                                 by Company),  whether Company  has a  joint
                                 or  other interest  or right  of any  other
                                 kind (including, without limitation,  goods
                                 in which  Company has an  interest or right
                                 as consignee),  and all accessions  thereto
                                 and  products  thereof  and  documents  and
                                 warehouse receipts therefor;

                       2.1.4     by way of floating charge, all book  debts,
                                 accounts, contract  rights, chattel  paper,
                                 instruments,  warehouse  receipts,  drafts,
                                 acceptances,   deposit  accounts,   general
                                 intangibles  and documents  of Company, and
                                 all   rights   in   and  to   all  security
                                 agreements,  deeds of  charge, leases,  and
                                 other  contracts   securing  or   otherwise
                                 relating to  any such book debts, accounts,
                                 contract     rights,     chattel     paper,
                                 instruments,   deposit  accounts,   drafts,
                                 acceptances   and  documents,   and   shall
                                 include, without  limitation, the  proceeds
                                 of  all  warranty  agreements  and  service
                                 contracts sold by or on behalf of Company;

                       2.1.5     by way  of floating  charge, all books  and
                                 records  (including,  without   limitation,
                                 computer  tapes, programs,  printouts,  and
                                 all  other computer  materials, records and
                                 electronic   data   processing    software)
                                 recording,  evidencing or  relating to  any
                                 or all of the foregoing;

                       2.1.6     by  way  of  floating  charge, all  deposit
                                 accounts  (and the investments and earnings
                                 thereof and documents evidencing the  same)
                                 into  which  the  proceeds  of  any  of the
                                 foregoing  may   from  time   to  time   be
                                 deposited; and

                       2.1.7     by  way of floating charge, all proceeds of
                                 any and  all of  the foregoing  (including,
                                 without  limitation,   cash  proceeds   and
                                 other  proceeds which  constitute  property
                                 of  the types described above)  and, to the
                                 extent   not   otherwise   included,    all
                                 payments    under   insurance,    or    any
                                 indemnity,  warranty or  guaranty,  payable
                                 by  reason   of  loss   or  damage  to   or
                                 otherwise  with   respect  to  any  of  the
                                 foregoing.

          3.      COVENANTS
                  ---------

                  3.1  The Company shall not without the consent in  writing
                       of the Chargee:

                       3.1.1     (except  for   charges  in  favour  of  the
                                 Chargee created  under or  pursuant to this
                                 Debenture) create  or permit to subsist any
                                 mortgage,  charge  or lien  on  any of  its
                                 undertaking or assets;

                       3.1.2     sell,   transfer,    hire-out,   lend    or
                                 otherwise  dispose of  its undertaking  and
                                 other assets  or any part  of them,  except
                                 by  getting in  and realizing  them in  the
                                 ordinary and  proper course of its business
                                 or as permitted by the Credit Agreement;

                  3.2  The Company shall:

                       3.2.1     give,  or   procure  the   giving,  to  the
                                 Chargee or  any person or persons appointed
                                 by  the   Chargee  for  this  purpose  such
                                 information (including  books and  records)
                                 as  to all  matters relating  to the Assets
                                 or otherwise  relating to  its business  or
                                 affairs  as  it  or  they shall  reasonably
                                 require and  access to all  premises as  it
                                 or   they  shall   reasonably  require   in
                                 accordance with the Credit Agreement;

                       3.2.2     deal  with  its  book  or  other  debts  or
                                 securities  for  money in  accordance  with
                                 the reasonable directions from the  Chargee
                                 from  time  to  time (which  directions can
                                 include assignments thereof  to the Chargee
                                 with notice to debtors) and, in absence  of
                                 such directions, to  get its book or  other
                                 debts  in and realize  them in the ordinary
                                 and proper  course of its  business but not
                                 (without  the  prior   permission  of   the
                                 Chargee)  by   means  of  factoring,  block
                                 discounting    or   any    other    similar
                                 arrangement;

                       3.2.3     upon  the occurrence of an Event of Default
                                 and until  such Event of  Default is waived
                                 in  writing  by  the Lenders  in accordance
                                 with the  Credit agreement,  pay into  such
                                 account  as  the  Chargee may  designate by
                                 notice  to the  Company from  time to  time
                                 all moneys which it may receive in  respect
                                 of  the book debts and other Assets charged
                                 by Clause 2; and

                       3.2.4     promptly notify  the Chargee of any meeting
                                 to discuss,  or any proposal or application
                                 for   the   appointment  of   a   receiver,
                                 liquidator or  similar official in  respect
                                 of the  Company or any  of its assets  and,
                                 if any  such official is  appointed, of his
                                 appointment.

                  3.3  If  the   Company  fails  to   perform  any  of   its
                       obligations  under  this  Debenture, the  Chargee may
                       take action as it may deem appropriate, on behalf  of
                       or  in the  name  of  the  Company or  otherwise,  to
                       perform or  to remedy  such failure  and recover  the
                       costs  and expenses so  incurred from  the Company on
                       demand.

          4.      MISCELLANEOUS
                  -------------

                  4.1  This Debenture shall be:

                       4.1.1     made  for   securing  present  and  further
                                 advances   and   shall  be   a   continuing
                                 security  to the  Chargee,  notwithstanding
                                 any settlement  of account or the existence
                                 at  any time  of  a  credit balance  or any
                                 other   matter,   act,   event   or   thing
                                 whatsoever;

                       4.1.2     without prejudice  and in  addition to  any
                                 other  security for  the Indebtedness which
                                 the Chargee,  any Collateral  Agent or  any
                                 Lender may hold now  or hereafter on all or
                                 any part of the Assets; and

                       4.1.3     in  addition  to  any  rights,  powers  and
                                 remedies at law.

                  4.2  No failure  or  delay on  the Chargee's  part in  the
                       exercise of  any of its  rights, powers and  remedies
                       under this  Debenture or at  law shall  operate or be
                       construed  as a  waiver.   No waiver  of any  of  the
                       Chargee's rights shall preclude any further or  other
                       exercise of that right or of any other right.

                  4.3  The  Chargee may  give time  or other  indulgence  or
                       make  any  other  arrangement,  variation or  release
                       with any  person in  respect of  the Indebtedness  or
                       any other security or guarantee for the  Indebtedness
                       without derogating  from the Company's liabilities or
                       the Chargee's rights under this Debenture.

                  4.4  The Company certifies  that neither the execution and
                       delivery of  this Debenture  and  the performance  of
                       the  covenants   contained  herein  nor  the  charges
                       created by  this Debenture  contravene any  provision
                       of its articles of  incorporation, bylaws or  any law
                       or  agreement binding  on it  or any  of the  Assets.
                       The  Company  covenants  with and  represents  to the
                       Chargee   that   the   documents  which   contain  or
                       establish   the   Company's   constitution    include
                       provisions  which   give  power,  and  all  necessary
                       corporate  authority has  been   obtained and  action
                       taken,  for   the  Company  to   grant  the   charges
                       contained  in this Debenture and execute and deliver,
                       and perform  the covenants  and obligations contained
                       in   this   Debenture   and   that   this   Debenture
                       constitutes  valid  and  binding  obligations of  the
                       Company  enforceable  in  accordance  with its  terms
                       except  as such  validity  or enforceability  may  be
                       limited  by  applicable  bankruptcy,  reorganization,
                       moratorium   or  other   insolvency  laws   affecting
                       creditors'   rights   generally   or   by   equitable
                       principles relating to enforceability.

                  4.5  Subject  only  to Clause  6,  on  final  payment  and
                       discharge of the Indebtedness and termination of  the
                       Commitment,  the Chargee  will,  at the  request  and
                       cost of  the Company,  release unto  the Company  the
                       property charged by or pursuant to these presents.

                  4.6  A certificate  of the Chargee as to the amount of the
                       Indebtedness from  time to time or  any of  it or any
                       other matter  connected  with  it or  this  Debenture
                       shall,  in   the  absence   of  manifest   error,  be
                       conclusive evidence of the facts stated in it.

                  4.7  The Company shall, on demand by the Chargee,  execute
                       and  deliver all such transfers, assignments or other
                       documents as the  Chargee may require to perfect  its
                       rights under  this Debenture or to give effect to any
                       sale or  disposal by  or on behalf of  the Chargee of
                       any of the Assets.

          5.      POWER TO CREDIT TO A SUSPENSE ACCOUNT
                  -------------------------------------

          Until payment and discharge in full of the Indebtedness any money
          received  hereunder may be  placed and kept for  such time as the
          Chargee  considers prudent  in  an interest  bearing separate  or
          suspense account in the name of such person as the Chargee thinks
          appropriate without any intermediate obligation to apply the same
          or  any  part thereof  in  or towards  discharge  of  any of  the
          Indebtedness.  Notwithstanding  any such payment in  the event of
          any  proceedings  in  or  analogous  to  bankruptcy, liquidation,
          receivership composition or arrangement the Chargee may prove for
          and agree to accept any dividend or composition or arrangement in
          respect of  the whole or any part of the Indebtedness in the same
          manner as if  the security constituted by this  Debenture had not
          been created.

          6.      AVOIDANCE OF PAYMENTS
                  ---------------------

          No  assurance,  security  or  payment  which  may be  avoided  or
          adjusted under any applicable law,  and no release, settlement or
          discharge given or made by  the Chargee on the faith of  any such
          assurance,  security or  payment, shall  prejudice or  affect the
          right of the Chargee to recover the Indebtedness in full from the
          Company (including any  moneys which it  may be compelled  by due
          process  of law to  refund pursuant to the  provisions of any law
          relating to  liquidation,  bankruptcy, insolvency  or  creditors'
          rights  generally and  any costs  payable by  it pursuant  to (or
          otherwise incurred in connection with such process) or to enforce
          the security created by or pursuant to this Debenture.

          7.      RECEIVER/REMEDIES
                  -----------------

                  7.1  Upon the  occurrence of an Event of Default and until
                       such Event  of Default  is waived in  writing by  the
                       Lenders in  accordance with the Credit Agreement, the
                       Chargee is hereby  authorized to take such action  as
                       it deems necessary, including:

                       a.   to sell all the  Company's title to  or interest
                       in the Assets  for such  consideration whatsoever  as
                       the Chargee may think fit, 

                       b.   with a view to  selling the Assets  (or offering
                       it  for sale)  to  repair, replace  and  develop  the
                       Assets and to  apply for any  appropriate permission,
                       license or approval;

                       c.   with a  view to  or in connection with  the sale
                       of the Assets, to  carry out any  transaction, scheme
                       or   arrangement  which  the   Chargee  may,  in  its
                       absolute discretion, consider appropriate;

                       d.   to insure the Assets  against such risks and for
                       such  amounts as  the Chargee  may  consider prudent;
                       and

                       e.   to do all or any of  the things or exercise  all
                       or any of the powers which are mentioned or  referred
                       to  herein,  any   other  document  executed  by  the
                       Company  or  applicable law  and  which  may  not  be
                       included in paragraphs (a) to (d) above.

                  7.2  Upon the  occurrence  of an  Event of  Default or  by
                       Statute,  the  Chargee may  by  writing  or  by  deed
                       appoint such  person or persons (including an officer
                       or officers  of the  Chargee) as it thinks  fit to be
                       Receiver of  the Assets  or any part  thereof and  in
                       the case of an appointment  of more than  one person,
                       to  act together  or  independently  of the  other or
                       others and the  Chargee may make such appointment  at
                       any time after the Agent  has demanded payment of the
                       Obligations  or if it  is requested  to do  so by the
                       Company or  upon the  presentation of  a petition  to
                       the  court for  an  order appointing  a  Receiver  in
                       respect of the Company.

                  7.3  Except as otherwise required by statute, the  Chargee
                       may  by  writing  or by  deed remove  a  Receiver and
                       appoint  another  in  his place  or  to  act  with  a
                       Receiver and the Chargee may  apply to the  court for
                       an order removing a Receiver.

                  7.4  The Receiver  shall be the  agent of  the Company and
                       the Company alone  shall be responsible for his  acts
                       and   defaults  and   liable  on  any   contracts  or
                       engagements made or  entered into or adopted by  him;
                       and in no  circumstances whatsoever shall the Chargee
                       be in  any way responsible for or incur any liability
                       in connection  with his contracts, engagements, acts,
                       omissions, misconduct,  negligence or  default and if
                       a liquidator of the  Company shall be  appointed, the
                       Receiver shall act as principal and not as agent  for
                       the Chargee.

                  7.5  The remuneration of the Receiver may be fixed by  the
                       Chargee  (and   may  be   or  include  a   commission
                       calculated by  reference to   the gross amount of all
                       moneys  received   or  otherwise   and  may   include
                       remuneration in  connection with  claims, actions  or
                       proceedings made or  brought against the Receiver  by
                       the  Company or any  other person  or the performance
                       or discharge  of any obligation  imposed upon him  by
                       statute or  otherwise) but such remuneration shall be
                       payable by the Company alone; and the amount of  such
                       remuneration may  be  debited  by  the Agent  or  the
                       Chargee to  any account of the Company, but shall, in
                       any  event,   form  part  of   the  Obligations   and
                       accordingly  be  secured  on  the  Assets  under  the
                       charges contained in this Debenture.

                  7.6  The Receiver, in addition  to any powers conferred on
                       a receiver or receiver/manager  by statute or  common
                       law, shall have the following powers:

                       (a)  to  enter upon, take  possession of,  get in and
                       collect the Assets  (or such part thereof in  respect
                       of which he may  be appointed) whether accrued before
                       or after the date of his appointment;

                       (b)  to sell, exchange, license, surrender,  release,
                       disclaim, abandon, return or otherwise dispose of  or
                       in any  way whatsoever  deal with the  Assets or  any
                       interest  in  the Assets  for such  consideration (if
                       any),  and  upon  such terms  (including  by deferred
                       payment or payment by  installments) as he  may think
                       fit and to concur in any such transaction;

                       (c)  to let on  charter, sub-charter, hire, lease  or
                       sell  on  condition and  to  grant  rights,  options,
                       licenses or  easements over the  whole or any part of
                       the Assets  and  (with or  without consideration)  to
                       rescind, surrender or disclaim or accept or agree  to
                       accept  surrenders  or  disclaimers  of leases,  hire
                       purchase  contracts  or  agreements  relating  to  or
                       affecting the Assets  in such circumstances, to  such
                       persons  (including,   without  limitation,  to   the
                       Chargee),  for  such  purposes and  upon  such  terms
                       whatsoever as  he may think fit  and also to vary the
                       terms of  any contract  affecting the  Assets and  to
                       act in  relation to any review of the rent or provide
                       payments under a  lease of the Assets in such  manner
                       as he may think fit;

                       (d)  to insure, protect,  decorate, maintain, repair,
                       alter, improve, replace,  exploit, the Assets or  any
                       part  thereof  in any  manner  and  for  any  purpose
                       whatsoever;

                       (e)  to   bring,  defend,   submit   to  arbitration,
                       negotiate,  compromise,   abandon   and  settle   any
                       claims,   disputes  and  proceedings  concerning  the
                       Assets or any part thereof;

                       (f)  to  transfer all  or any  of  the Assets  to any
                       other  company  or  body  corporate, whether  or  not
                       formed or acquired for the purpose;

                       (g)  to redeem,  discharge or  compromise any  charge
                       from time to time having priority to or ranking  pari
                       passu with this Debenture;

                       (h)  in connection  with the exercise  of any of  his
                       powers, to  execute or do,  or cause  or authorize to
                       be executed or done,  on behalf of or in the name  of
                       the Company  or otherwise, as he  may think fit,  all
                       documents,  receipts,  registrations, acts  or things
                       which he may consider appropriate;

                       (i)  to exercise  any powers,  rights or entitlements
                       in relation  to any  of the  Assets or incidental  to
                       the ownership  of or rights in  or to  any Assets and
                       to complete, disclaim,  abandon or modify all or  any
                       of the outstanding  contracts or arrangements of  the
                       Company relating to or affecting the Assets;

                       (j)  generally to  carry out,  or cause or  authorize
                       to  be  carried   out,  any  transaction,  scheme  or
                       arrangement  whatsoever,  whether  similar or  not to
                       any of  the  foregoing,  in  relation to  the  Assets
                       which he may consider expedient.

                  7.7  No purchaser from, or other person dealing with,  the
                       Chargee  or   the  Receiver  shall  be  concerned  to
                       enquire  whether  any  of  the  powers  exercised  or
                       purported  to  be  exercised  has  arisen  or  become
                       exercisable,   whether    the   Obligations    remain
                       outstanding, whether  the Receiver  is authorized  to
                       act  or  as  to  the  propriety or  validity  of  the
                       exercise or purported exercise  of any power; and the
                       title of  such a purchaser and the position of such a
                       person shall not  be impeachable by reference to  any
                       of those matters. 

                  7.8  The receipt  of the Chargee  or the Receiver shall be
                       an  absolute  and   a  conclusive   discharge  to   a
                       purchaser and shall relieve  him of any obligation to
                       see to  the application of any  moneys paid  to or by
                       the direction of the Chargee or the Receiver.

                  7.9  Neither the  Chargee  nor  the  Receiver nor  any  of
                       their affiliates  shall be liable  to the Company  in
                       respect of any  loss or  damage which  arises out  of
                       the exercise  or the failure to exercise any of their
                       respective powers.

                  7.10 Entry into possession of  the Assets shall not render
                       the  Chargee or  the Receiver  liable to  account  as
                       mortgagee  in possession;  and  if  and whenever  the
                       Chargee  enters  into possession  of  the  Assets, it
                       shall  be entitled  at any  time to  go  out  of such
                       possession.

                  7.11 The Company  hereby agrees  to indemnify the  Chargee
                       and  the  Receiver   from  and  against  all  losses,
                       actions,  claims,  costs   (including  legal  costs),
                       expenses,   demands   and   liabilities  whether   in
                       contract,  tort,   or  otherwise   now  or  hereafter
                       sustained or incurred by  the Chargee or the Receiver
                       or  by  any  person  for  whose  liability,  act   or
                       omission  the   Chargee  or   the  Receiver  may   be
                       answerable,  in  connection  with  anything  done  or
                       omitted under this Debenture,  or in the  exercise or
                       purported exercise  of the  powers herein  contained,
                       or occasioned by any  breach by the Company of any of
                       its covenants  or other obligations  to the  Chargee,
                       or in  consequence of any  payment in  respect of the
                       Obligations (whether made  by the Company or a  third
                       person) being  declared  void  or impeached  for  any
                       reason whatsoever.

                  7.12 The  Company further  covenants with  the Chargee  at
                       the Company's own cost,  as a continuing security for
                       the payment or discharge of the Obligations:

                       (a)  if  the  Chargee,  in  its absolute  discretion,
                       considers that  all or any of the Assets is in danger
                       of being  seized or sold under  any form of  distress
                       or execution levied or  threatened or is otherwise in
                       jeopardy or if any circumstance shall occur which  in
                       the opinion  of  the  Chargee  is prejudicial  to  or
                       imperils or  is likely to  prejudice or   imperil any
                       or all  of the security hereby created or recovery of
                       the  Obligations and so requires, promptly to execute
                       a  first or subsequent  fixed charge  (as the Chargee
                       may require)  in terms  specified by  the Chargee  of
                       all or any part of the  Assets which is for  the time
                       being  subject to  the floating  charge  contained in
                       this Debenture;

                       (b)  if  the Chargee so requires, promptly to execute
                       an assignment  to the Chargee  in terms specified  by
                       the Chargee of all or any debts or  moneys payable to
                       the Company and any Charges or documents relating  to
                       them  or  otherwise  to  negotiate  the  same to  the
                       Chargee;

                  7.13 The  Company further covenants  with the Chargee from
                       time  to time  (and,  for  the purposes  mentioned in
                       paragraph   (a)   below,  notwithstanding   that  the
                       Chargee may not have served  a demand for  payment of
                       the Obligations)  upon  demand  to  execute,  at  the
                       Company's own  cost, any  document or do  any act  or
                       thing which:

                       (a)  the  Chargee   may  specify   with  a  view   to
                       perfecting  or   improving  any  charge  or  security
                       created or intended to be created by this  Debenture;
                       or

                       (b)  the Chargee or the  Receiver may specify  with a
                       view to  facilitating the   exercise or the  proposed
                       exercise of any of their powers.

                  7.14 The  Company   covenants  to   register  the  charges
                       contained in  this Debenture  against the  registered
                       title of any registered charge hereby affected.

                  7.15 In addition and without  prejudice to any other event
                       resulting  in   a  crystallisation  of  the  floating
                       charge created by this  Debenture or any  other right
                       the Chargee  may have, the  Chargee may,  at any time
                       or from  time to time whether  or not it has served a
                       demand for payment  of the Obligations, by notice  in
                       writing  to the  Company  declare that  the  floating
                       charge  hereby  created  shall be  converted  into  a
                       first  specific  fixed  charge   as  to  all  of  the
                       undertaking, property and  assets or such of them  as
                       may  be  specified  in  the  notice, and  by  way  of
                       further  assurance, the Company, at  its own expense,
                       shall execute  all  documents  in  such form  as  the
                       Chargee  shall  require  and  shall  deliver  to  the
                       Chargee all  deeds, certificates  and documents which
                       may be necessary to perfect the first specific  fixed
                       charge.

                  7.16 In addition and without prejudice to any other  event
                       resulting  in   a  crystallisation  of  the  floating
                       charge, the  floating charge  contained herein  shall
                       automatically be converted into a fixed charge over:

                       (a)  all  property,  assets  or  undertaking  of  the
                       Company subject to the floating charge, if and when:

                            (i)  the Company  ceases to carry on business or
                                 a substantial  part thereof  or shall cease
                                 to be a going concern;

                            (ii) the Company  stops making  payments to  its
                                 creditors  or  gives  notice  to  creditors
                                 that it intends to stop payment;

                           (iii) if the holder  of any other  Charge whether
                                 ranking in priority to  or pari passu  with
                                 or  after  the  charges  contained in  this
                                 Debenture  shall  appoint   a  receiver  or
                                 receiver/manager; or

                            (iv) an  Event  of  Default occurs  and  (A) the
                                 Agent  declares  all  Indebtedness  to   be
                                 immediately due  and payable  or (B)  gives
                                 notice  to   the  Borrower   Representative
                                 stating  that the Floating charge hereunder
                                 has become fixed.

                       (b)  any  property,  assets  or  undertaking  of  the
                       Company which shall become subject to a Charge  other
                       than a  Permitted Lien in favor  of any person  other
                       than the Agent  or any  Chargee or  which is/are  the
                       subject of a sale,  transfer or other disposition, in
                       either case, contrary  to the covenants contained  in
                       this  Debenture,  immediately  prior  to such  Charge
                       arising or  such sale, transfer  or other disposition
                       being made.

                  7.17 The  Company  irrevocably   appoints  each   Receiver
                       jointly and  also severally  to be  its attorney  and
                       attorneys  (with  full  power to  appoint substitutes
                       and to  sub-delegate, in both  cases, with regard  to
                       all  or any  part  of  the Assets)  on behalf  of the
                       Company and in its name  or otherwise, to execute any
                       document or  do any  act or thing which  the Receiver
                       (or their  substitutes or delegates)  may, in its  or
                       his  absolute  discretion,  consider  appropriate  in
                       connection with  the exercise of any of the powers of
                       the Chargee or  the Receiver or which the Company  is
                       obliged  to the  Chargee to  execute or  do,  whether
                       under  this   Debenture  or  otherwise;  and  without
                       prejudice to the  generality of its power to  appoint
                       substitutes  and  to  sub-delegate,  the Chargee  may
                       appoint the Receiver  as its substitute  or delegate,
                       and  any  person  appointed  the  substitute  of  the
                       Chargee  shall, in  connection with  the  exercise of
                       the  said  power of  attorney,  be  the agent  of the
                       Company. 

                  7.18 For the purpose of giving   effect to this Debenture,
                       the Company  hereby declares  that, as  and when  the
                       charges  contained  in  this  Debenture shall  become
                       enforceable   or  a   demand  for   payment   of  the
                       Obligations has  been made,  it will hold all  of the
                       Assets  (subject to  the  right of  redemption)  upon
                       trust to  convey, assign or  otherwise deal with  the
                       Assets  in  such  manner and  to such  person  as the
                       Chargee shall  direct and declares  that it shall  be
                       lawful for  the Chargee to  appoint a  new trustee or
                       trustees of the Assets in place of the Company.

                  7.19 If under any applicable law,  whether as a  result of
                       a judgment against the  Company or the liquidation of
                       the  Company or  for any  other reason,  any  payment
                       under  or in connection  with this  Debenture is made
                       or any  amount is received  or recovered by the Agent
                       or the  Chargee in  respect of the  Obligations in  a
                       currency  (the   OTHER  CURRENCY)   other  than   the
                       currency in  which the Obligations  are payable  (the
                       ORIGINAL  CURRENCY),  then  to the  extent  that  the
                       payment to or  receipt by  the Agent  or the  Chargee
                       (when converted  at the rate  of exchange on the date
                       of payment  or receipt) falls short  of the whole  of
                       the Obligations the  Company shall as a separate  and
                       independent  obligation fully  indemnify the  Chargee
                       against  the amount  of the  shortfall; and  for  the
                       purposes of this clause,  RATE OF EXCHANGE  means the
                       rate at  which the  Chargee is  able on the  relevant
                       date to  purchase  the  original currency  in  London
                       with the other currency.

                  7.20 If the  Company fails to pay or discharge any part of
                       the  Obligations when due,  the Agent  or the Chargee
                       from  time  to  time may  purchase an  amount  of the
                       currency  in which  such sum  is due  with any  other
                       currency or  currencies and  the Company's obligation
                       thereafter shall  be to pay to the Chargee the amount
                       of  the  other currency  or  currencies  so  used  to
                       purchase.

                  7.21 The  amount secured  or to be  ultimately recoverable
                       under  this  security  is unlimited.    This security
                       shall be  stamped in  the first  instance with  stamp
                       duty  covering  an  indebtedness  of  $15,000,000  in
                       lawful currency of the  United States of  America and
                       the Chargee shall be and  is hereby empowered  at any
                       time or times hereafter  (without further license  or
                       consent  of the  Company) to  affix  additional stamp
                       duty  hereon  covering  any   sum  or  sums   or  the
                       equivalent in lawful currency of Barbados or any  sum
                       or  sums by which  the Indebtedness  and liability of
                       the Company  to the Chargee  may exceed  the said sum
                       and to  execute either in the name of  the Company or
                       in  its own  name and  lodge  with the  Registrar  of
                       Companies  for  Registration amended  particulars  of
                       the Charge stating  the increased maximum sum  deemed
                       to be secured by  the charge  it being the intent  of
                       these  presents that  until its discharge  in writing
                       by the  Chargee the charge  hereby created shall be a
                       continuing security covering  the full amount  of the
                       Indebtedness  and  liability  at   any  time  of  the
                       Company to the Chargee.

                  7.22      (a)  The obtaining of a judgment or judgments in  
                       any action to enforce this security or any  covenants
                       herein contained  shall not  operate as  a merger  of
                       this security or of the  moneys hereby secured or any
                       of the said  covenants or affect the Chargee's  right
                       to interest  at the  rate and time  herein set  forth
                       (or set forth in the Credit  Agreement) on any of its
                       rights under the said covenants;

                            (b)  The Chargee shall not be answerable for any
                       loss or  damage happening in or about the exercise or
                       execution  of  any  power  conferred  on  the Chargee
                       howsoever  or  by   law  implied  or  of  any   trust
                       connected thereto nor shall  the Chargee be deemed as
                       being in  possession when entering  to inspect or  to
                       effect repairs or remedy breaches.


          8.      COSTS
                  -----

          All costs, charges and expenses  properly incurred by the Chargee
          and  all  other  moneys paid  by  the  Chargee  in perfecting  or
          otherwise in connection with this  Debenture and all costs of the
          Chargee of  all proceedings  for  enforcement of  this  Debenture
          shall  be recoverable  from  the Company  as a  debt,  shall bear
          interest at the  same rate from time to  time as the Indebtedness
          (as well before  as after judgment), and shall be  charged on the
          Assets.

          9.      SEVERANCE
                  ---------

          If at  any time  any provision  in this  Debenture is  or becomes
          invalid, illegal  or  unenforceable, the  validity, legality  and
          enforceability  of the  remaining  provisions of  this  Debenture
          shall not be impaired.

          10.     NOTICES
                  -------

          Any notice required  under this Agreement  shall be given  in the
          manner prescribed in the aforesaid Credit Agreement.

          11.     LAW
                  ---

          This Debenture shall  be governed by and construed  in accordance
          with laws of Barbados.

          12.     BINDING AGREEMENT
                  -----------------

          This Debenture shall be binding on the Company and its successors
          and shall inure to the benefit of the Chargee and  its successors
          and assigns.


          IN WITNESS WHEREOF this Debenture was entered into as a Deed the
          day and year first above written.

          THE COMMON SEAL of MUREX         )
          DIAGNOSTICS CORPORATION was      )
          hereunto set and affixed by      )    (SEAL)
          the Corporate Secretary and      )
          the Secretary thereof in the     )
          presence of:                     )         Countersigned
                                              THE CORPORATE SECRETARY LIMITED
          /s/ Noble E.G. Powers
                                                  /s/ Mary Ellen Bourque
                                 )
          /s/ Allan Lewis        )  Directors           Secretary
                                 )

          Witness:  /s/ Vere P. Brathwaite
          Name:  VERE P. BRATHWAITE
          Description:  ATTORNEY-AT-LAW


          THE COMMON SEAL of MUREX           )
          DIAGNOSTICS INTERNATIONAL INC      )
          was hereunto set and affixed by    )    (SEAL)
          the Corporate Secretary and        )
          the Secretary thereof in the       )
          presence of:                       )         Countersigned
                                              THE CORPORATE SECRETARY LIMITED
          /s/ Noble E.G. Powers
                                                  /s/ Mary Ellen Bourque
                                 )
          /s/ Allan Lewis        )  Directors            Secretary
                                 )

          Witness:  /s/ Vere P. Brathwaite
          Name:  VERE P. BRATHWAITE
          Description:  ATTORNEY-AT-LAW


          EXECUTED AND DELIVERED:          )
          as a Deed on behalf of           )
          BANK OF AMERICA, F.S.B.          )
          the Chargee by:

          /s/ John Yankauskas, VP

          NOTARY PUBLIC
          
          <PAGE>

          NOTARY PUBLIC

          I, Laura Cantrell Notary Public in and for the state of Georgia
          do hereby CERTIFY that on the day of the date hereof personally
          came and appeared before me John Yankauskas to me made known by
          due identification to be named and described in the above written
          Debenture and did in my presence sign seal and deliver the same
          as and for free and voluntary Act and Deed and I further CERTIFY
          the same under my hand and Seal of Office hereto set and affixed
          this 12th day of November one thousand nine hundred and ninety-
          six.


                            NOTARY PUBLIC


                                 /s/ Laura Cantrell

                                 Notary public, Rockdale County, Georgia
                                 My Commission Expires June 23, 1998