Exhibit 10.1

                           FOURTH AMENDMENT TO LEASE

      THIS FOURTH  AMENDMENT  TO LEASE made as of this 9th day of October  1998,
(hereinafter   referred  to  as  this   "Amendment"),   between  ALFRED  SANZARI
ENTERPRISES,  L.P., having an office c/o Alfred Sanzari Enterprises, Court Plaza
North,  25 Main Street,  6th Floor,  Hackensack,  new Jersey 07601  (hereinafter
referred to as "Landlord"),  and BIO-REFERENCE LABORATORIES,  INC., a New Jersey
corporation,  having an office at 481 Edward H. Ross Drive,  Elmwood  Park,  New
Jersey 07407 (hereinafter referred to as "Tenant").
                             W I T N E S S E T H:
      WHEREAS, Alfred Sanzari (Landlord's predecessor-in-interest),  as landlord
(hereinafter  referred  to as  "Sanzari"),  and  Pharmadyne  Laboratories,  Inc.
(Tenant's  predecessor-in-interest),  as  tenant  (hereinafter  referred  to  as
"Pharmadyne"),  heretofore  entered  into a certain  written  Lease  dated as of
November  7, 1978,  wherein and whereby  Landlord  leased to Tenant,  and Tenant
hired from Landlord,  certain premises  consisting of  approximately  thirty-one
thousand five hundred twenty-seven  (31,527) square feet (hereinafter  sometimes
referred  to as the  "Original  Premises"  or the  "Premises"),in  the  building
located at 481 Edward H. Ross Drive,  in the Borough of Elmwood Park,  county of
Bergen and State of New Jersey (hereinafter  referred to as the "Building"),  as
more  particularly  described  therein,  for a term which  commenced on March 1,
1979,  and was  scheduled to expire on February 28, 1989,  at the Basic Rent and
additional  rent,  and upon the terms,  covenants,  conditions,  provisions  and
agreements contained in said Lease; and
      WHEREAS,  said Lease was modified by that certain First Amendment to Lease
dated  November 1, 1979,  wherein and whereby,  inter alia,  Landlord and Tenant
settled certain disputes; and


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      WHEREAS,  said Lease and the interest of Pharmadyne as tenant  thereunder,
was assigned to CL Laboratories of New Jersey, Inc.  (hereinafter referred to as
"CL"),  pursuant to that certain  Assignment and  Assumption of Lease  Agreement
dated December 10, 1981; and
      WHEREAS,  said Lease was further modified by that certain  Agreement dated
as of March  23,  1988,  wherein  and  whereby,  inter  alia,  the Lease and the
interest  of  CL  as  tenant  thereunder,  was  assigned  to  Med-Mobile,   Inc.
(hereinafter  referred  to as  "Med-  Mobile"),  and the term of the  Lease  was
extended for a further period of five (5) years, commencing on March 1 1989, and
expiring on February 28, 1984; and
      WHEREAS,  said Lease was further modified by that Certain Second Amendment
to Lease dated as of March 23, 1988; and
      WHEREAS,  said Lease was  modified by that Third  Amendment to lease dated
January 31, 1992, wherein and whereby,  inter alia,  Landlord and Tenant settled
certain  defaults  by  Tenant  under  the  Lease  and  discontinued   litigation
instituted by Landlord against Tenant in connection therewith; and
      WHEREAS, on or about November 15, 1989, Med-Mobile changed its
name to Tenant; and
      WHEREAS,  said Lease was further  modified by that certain Third Amendment
to Lease dated as of February 28, 1994,  wherein and  whereby,  inter alia,  the
term  of the  Lease  was  extended  for a  further  period  of five  (5)  years,
commencing on March 1, 1994, and expiring on February 28, 1999; and
      WHEREAS,  said  Lease,  as so  modified,  and as the same  may  have  been
otherwise amended and/or modified,  is hereinafter  collectively  referred to as
the "Lease"; and

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      WHEREAS,  Landlord and Tenant  desire to further  modify the Lease only in
the respects hereinafter stated.
      NOW THEREFORE,  in  consideration of the premises demised by the Lease and
the mutual  covenants  hereinafter  contained  and for other  good and  valuable
consideration,  the receipt and  adequacy of which is hereby  acknowledged,  the
parties hereto by these presents do covenant and agree as follows:
      1. The  recital  clauses  set forth  above  shall be deemed a part of this
Amendment as though set forth verbatim and at length herein.
      2. Except as otherwise  expressly set forth herein,  all capitalized terms
in this Amendment shall have the meanings set forth for such terms in the Lease.
      3. A. The "Term" of the Lease (as defined in  Paragraph B of Schedule  "C"
attached to the Lease)  shall be deemed to be further  extended  for a period of
vive (5) years,  commencing  March 1, 1999, to and including  February 28, 2004,
inclusive,  upon the terms,  covenants,  conditions,  provisions  and agreements
contained in the Lease, as modified by this Amendment.
            B.  Effective  as of March 1,  1999,  "Basic  Rent" (as  defined  in
Paragraph A of Schedule "C" attached to the Lease) shall be deemed to be the sum
of Two Hundred Twenty Thousand Six Hundred Eighty-Nine and 00/100  ($220,689.00)
Dollars per annum,  payable in equal monthly  installments of Eighteen  Thousand
Three Hundred Ninety and 75/100 ($18,390.75) Dollars each.
      4.    A.    (1)   Effective as of the date Landlord delivers
possession of the "Additional Space" (as hereinafter defined)
(hereinafter referred to as the "Additional Space Commencement
Date"), Landlord hereby leases to Tenant, and Tenant hereby hires
from Landlord, a portion of the building located at 487 Edward H.

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Ross Drive,  Borough of Elmwood  Park,  County of Bergen and State of New Jersey
(hereinafter   referred  to  as  the   "Adjacent   Building"),   consisting   of
approximately  twenty-four  thousand  (24,000) square feet, as shown on the plan
attached hereto and made a part hereof as Schedule "A-1"  (hereinafter  referred
to as the "Additional Space").
                  (2) The  "Demised  Premises"  (as  defined in Article 1 of the
Lease) shall be and be deemed to be: "(I) a portion of the Building,  consisting
of approximately  thirty-one thousand five hundred twenty-seven (31, 527) square
feet, as shown on Schedule "A" attached to the Lease;  and (ii) a portion of the
Adjacent  Building,  consisting of approximately  twenty-four  thousand (24,000)
square feet, as shown on Schedule "A-1" attached hereto."
            B.    Effective as of the Additional Space Commencement
Date, the following shall be applicable solely with respect to the
Additional space:
                  (1) "Basic  Rent" (as defined in  Paragraph A of Schedule  "C"
attached to the Lease)  shall be deemed to be the sum of One  Hundred  Fifty-Six
Thousand and 00/100  ($156,000.00)  Dollars per annum,  payable in equal monthly
installments of Thirteen Thousand and 00/100 ($13,000.00) Dollars each.
                  (2)  "Proportionate  Share'  (as  defined  in  Paragraph  E of
Schedule "C" attached to the Lease)  shall be deemed to be  "twenty-five  (25%)(
percent/"
                  (3) The number of parking  spaces  provided in  Paragraph 4 of
the Third  Amendment to Lease dated as of February 28, 1994,  shall be deemed to
be "twenty (20)", a shown on the plan attached  hereto and made a part hereof as
Schedule "A-2."

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                  (4) Wherever in the Lease  reference is made to the "Building"
or the "building," same shall be deemed to be the Adjacent Building.
            (C) (1) Tenant has examined and inspected the  Additional  Space and
agrees to accept the same in the condition in which it exists on the  Additional
Space Commencement Date. Tenant hereby acknowledges and agrees that no materials
whatsoever  are to be  furnished  by  Landlord  and no  work  whatever  is to be
performed  by  Landlord in  connection  with said  Additional  Space or any part
thereof.
            (2) (I) Tenant agrees, at Tenant's sole cost and expense, to perform
all work in accordance with plans and  specifications  to be prepared by Tenant,
at Tenant's  sole cost and expense,  and  thereafter,  delivered to Landlord for
Landlord's  approval,   which  approval  shall  not  be  unreasonably   withheld
(hereinafter referred to as "Tenant's Additional Space Work").
                  (ii)  Tenant's  Additional  Space Work shall be  performed  in
accordance  with  all  applicable  laws  and in  good  and  workmanlike  manner,
utilizing  new and  first-class  materials.  Tenant  shall obtain and deliver to
Landlord all  "sign-offs"  and  approvals in  connection  therewith,  including,
without limitation, a certificate of occupance.
                  (iii) (a) Tenant  acknowledges  and agrees that Landlord shall
have the right to submit a bid for the performance of Tenant's  Additional Space
Work.
                              (b)   In the event Tenant selects Landlord
to perform Tenant's  Additional Space Work,  Tenant agrees to pay Landlord,  the
total cost of Tenant's Additional Space work, as follows:  (x) twenty-five (25%)
percent  shall be paid by Tenant  to  Landlord  upon  commencement  of  Tenant's
Additional Space Work, as

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additional  rent, upon demand therefor;  (y) twenty-five  (25%) percent shall be
paid by Tenant to Landlord upon completion of Tenant's Additional Space Work, as
additional rent, upon demand therefor; and (z) fifty (50%) percent shall be paid
by Tenant to Landlord,  by increasing  the Basic Rent reserved and covenanted to
be paid by Tenant to Landlord under the Leae, as modified by this Amendment,  by
the annual amount required to fully amortize such amount over sixty (60) months,
plus  interest,  at the rate of ten (10%)  percent  per annum,  in which  event,
Landlord  and Tenant  shall  execute  and  deliver  to each  other an  agreement
modifying  the Lease  (including  this  Amendment),  setting forth the increased
Basic Rent,  but such  increase  shall  nevertheless  be effective  even if such
agreement is not executed and delivered.
                        (iv)  Tenant shall be required to utilize
Landlord or the  contractors  designated  by Landlord  with  respect to any work
which involves penetrating or altering the exterior, facade, floor slab, roof or
structure of the Building  which Tenant  desires to perform in  connection  with
Tenant's  Additional  Space  Work  (or  any  other  work  in and to the  Demised
Premises),  provided  that  the  cost  charged  by  Landlord  or the  contractor
designated  by Landlord is not greater than ten 910%)  percent of the lowest bid
received by Tenant in a competitive bid for the same scope of work. In the event
the cost charged by Landlord or the contractor designated by Landlord is greater
than ten (10%) percent of the lowest bid received by Tenant as  aforesaid,  then
Tenant shall be entitled to retain its own  contractors  to perform  which work,
subject to the prior written  approval of Landlord,  which approval shall not be
unreasonably withheld or delayed.
                  (3)   (I)   Landlord shall be liable and responsible
for the costs of compliance with any environmental laws [including,

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without limitation,  the Industrial Site Recovery Act, N.J.S.A. 13:1k-6 ET SEQ.,
and the regulations promulgated thereunder (hereinafter collectively referred to
as "ISRA")] for spills or  discharges of  "hazardous  substances"  or "hazardous
wastes" (as such terms are defined under such environmental laws) which occurred
in or to the Additional  Space prior to the Additional  Space Term  Commencement
Date and which  were not  caused in whole or in part,  by Tenant or its  agents,
servants, employees, contractors or representatives.
                        (ii)  Landlord shall indemnify and hold Tenant
harmless from and against any and all claims and liabilities (including, but not
limited  to,  reasonable  attorneys'  fees)  which may be  incurred by Tenant in
connection  with,  or arising out of  Landlord's  obligations  contained  in (I)
hereof.
      5.    Effective as of the date hereof:
            A.    Article 40 of the Lease shall be deemed to be
deleted, and the following inserted in its place:
      "40.  RENEWAL OPTION:
            ---------------
            A. Subject to the provisions set forth below,  Tenant shall have the
            option to renew this Lease for an additional  term of five (5) years
            (hereinafter  referred to as the "Renewal Term"), which Renewal Term
            shall  commence  upon  the  expiration  of the  term of  this  Lease
            (hereinafter  referred to as the "Initial Term").  All of the terms,
            covenants  and  conditions  of this Lease  shall  govern the Renewal
            Term,  except as otherwise  specifically set forth hereinafter or if
            APPLICABLE thereto:

                        (1) The Annual  Basic Rent shall be the  greater of: (I)
            the "Market Rent" (as defined in subsection (2) hereof); or (ii) the
            Basic Rent and  additional  rent which was in effect during the last
            year of the Initial Term.

                        (2) "Market Rent" shall mean the
            fair market rent for the Premises for the
            Renewal Term, determined as of the date one

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            hundred  eighty  (180) days prior to the  expiration  of the Initial
            Term (hereinafter  referred to as the "Determination  Date"),  based
            upon the rents  generally  in effect  for  comparable  condition  in
            Bergen  County,  New  Jersey.  Market  Rent  (for  the  purposes  of
            determining the Basic Rent only during the commonly known as a "net"
            basis;  that is, in  computing  Market Rent it shall be assumed that
            all real estate taxes and customary  services are excluded from such
            Basic Rent.

                        (3) Landlord shall notify Tenant  (hereinafter  referred
            to as "Landlord's Determination Notice") of Landlord's Determination
            Notice") of Landlord's determination of the Market Rent within sixty
            (60)  days of the  Determination  Date.  If  Tenant  disagrees  with
            Landlord's determination,  Tenant shall notify Landlord (hereinafter
            referred to as "Tenant's Notice of Disagreement") within thirty (30)
            days of receipt of Landlord's Determination Notice. Time shall be of
            the essence with respect to Tenant's Notice of Disagreement, and the
            failure of Tenant to give such  notice  within  the time  period set
            forth above shall  conclusively be deemed an acceptance by Tenant of
            the Market Rent as  determined by Landlord and a waiver by Tenant of
            any right to dispute  such Market Rent.  If Tenant  timely gives its
            Tenant's  Notice of  disagreement,  then the  Market  Rent  shall be
            determined as follows:  Landlord and Tenant shall, within thirty (30
            days of the date on which Tenant's Notice of Disagreement was given,
            each appoint "Appraiser" (as hereinafter defined) for the purpose of
            determining the Market Rent. An "Appraiser" shall mean either: (1) a
            duly qualified  impartial  real estate  appraiser who is a member of
            the  American  Institute  of Real Estate  Appraisers  and who has at
            least ten (1) years  experience  in  appraising  the rental value of
            industrial/warehouse  properties  comparable  to  the  Building  and
            located in Northern New Jersey;  or (ii) a New Jersey  licensed real
            estate broker for a period in excess of ten (1) years and who has at
            least ten 91) years experience in leasing industrial/warehouse space
            in  buildings  comparable  to the  Building  located in Northern New
            Jersey.  In the event that the two 92)  Appraisers so appointed fail
            to agree ass to the Market  Rent  within a period of thirty (3) days
            after  the  appointment  of  the  second  Appraiser,  such  two  92)
            Appraisers shall forthwith  appoint a third Appraiser who shall make
            a determination  in the manner  hereinafter  described within thirty
            93) days thereafter.

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            If such two (2) Appraisers  fail to agree upon such third  Appraiser
            within ten (1) days  following the last thirty 93) day period,  such
            third Appraiser  shall be appointed by the Bergen County  Assignment
            Judge of the New Jersey Superior  Court.  Such two (2) Appraisers or
            the third  Appraiser,  as the case may be,  shall  proceed  with all
            reasonable  dispatch to determine  the Market Rent.  Within  fifteen
            915) days  following the  appointment of the third  Appraiser,  each
            party shall submit to the third  Appraiser a written  report setting
            forth its  determination  of the  market  Rent,  together  with such
            information  on comparable  rentals,  or such other evidence as such
            party shall deem relevant.  The third Appraiser shall, within thirty
            (30) days  following the  submission of such written  reports render
            its decision by selecting the determination of Market Rent submitted
            by  either  the  Appraiser  selected  by  Landlord  or the  Appraise
            selected by Tenant which,  in the judgement of the third  Appraiser,
            most nearly  reflects  the Market Rent.  It is expressly  understood
            that such third Appraiser shall have no power or authority to select
            any Market Rent other than a Market Rent  submitted by the Appraiser
            selected by Landlord or the  Appraiser  selected by Tenant,  and the
            decision of such third Appraiser shall be final and binding upon the
            parties hereto.  The decision of such Appraisers shall be final, and
            such  decision  shall be in writing  and a copy  shall be  delivered
            simultaneously to Landlord and to Tenant. If such Appraisers fail to
            deliver their decision as set forth above prior to the  commencement
            of the Renewal Term,  Tenant shall pay Landlord the Basic Rent which
            was in effect as of the last day of the  Initial  Term,  until  such
            decision is so delivered.  If the Market Rent as determined above is
            in excess of the actual rent paid, then Tenant,  upon demand,  shall
            pay to Landlord the difference  between the actual rent paid and the
            Market Rent from the commencement of the Renewal Term.  Landlord and
            Tenant  shall each be  responsible  for and shall pay the fee of the
            Appraiser  appointed by them  respectively,  and Landlord and Tenant
            shall share equally the fee of the third Appraiser.

                  B.    Tenant's option to renew, as
            provided in subparagraph A hereof, shall be
            conditioned upon and subject to each of the
            following:

                        (1)  Tenant  shall  notify  Landlord  in  writing of its
            exercise of its option to renew at least  twelve (12) months but not
            more than

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            fifteen (15) months prior to the expiration of
            the Initial Term;

                        (2) At the time  Landlord  receives  Tenant's  notice as
            provided in  subsection  91) hereof and at the  commencement  of the
            Renewal Term:  (I) Tenant shall not be in default under the terms of
            provisions of this Lease;  and (ii) Tenant shall not have  subleased
            fifty (50%) percent or more of the Premises,  exclusive of subleases
            to any parent, subsidiary or affiliate of Tenant;

                        (3) Tenant  shall have no further  renewal  option other
            than the option to renew this Lease for the one (1) Renewal  Term as
            set forth in subparagraph A hereof;

                        (4) This  option to renew  shall be deemed  personal  to
            Tenant and may not be assigned or transferred,  except in connection
            with an assignment  effectuated in accordance with the provisions of
            Article 12 hereof; and

                        (5) Landlord  shall have no obligation to do any work or
            perform  any  services  for the  Renewal  Term with  respect  to the
            premises,  which  Tenant  agrees  to  accept  in its  then  "as  is"
            condition)"

            B.    The following paragraphs shall be deemed to be

added to the Lease as Articles 41 through 44 thereof:

            "41.  NO  MONEY  DAMAGES:  If in  this  Lease  it is  provided  that
            Landlord's  consent  or  approval  as to  any  matter  will  not  be
            unreasonably  withheld,  and it is  established  by a court  or body
            having  final   jurisdiction  there  over  that  Landlord  has  been
            unreasonable,  then  Landlord  shall be  deemed  to have  given  its
            consent or approval  and, in  addition  thereto,  shall be liable to
            Tenant for money damages [excluding,  however, consequential damages
            (e.g.,  lost profits or loss of business)] by reason of  withholding
            its  consent,  if such court or body  specifically  determined  that
            landlord has acted in bad faith or maliciously  (the burden of which
            shall be  Landlord's  responsibility  to prove that landlord has not
            acted  in bad  fair or  maliciously),  subject  nevertheless  to the
            provisions of Article 36 hereof."

            "42.  HOLDING OVER:     If Tenant retains
                  ------------
            possession of the Premises or any part
            thereof, after the termination of the term by
            lapse of time or otherwise, without prior
            written approval of Landlord, Tenant shall pay

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            Landlord,  two 92) times the  monthly  Basic Rent  payable by Tenant
            during the last full  month of the term,  together  with  additional
            rent and other charges as provided herein,  for the time Tenant thus
            remains in possession,  and, in addition thereto, shall pay Landlord
            all damages, consequential as well as direct, sustained by reason of
            Tenant's retention of possession. If Tenant remains in possession of
            the Premises or any part thereof,  after the termination of the term
            by lapse of time or  otherwise,  such  holding  over  shall,  at the
            election of Landlord expressed in a written notice to Tenant and not
            otherwise, constitute an extension of this lease on a month-to-month
            basis,  at two (2) times the  monthly  Basic Rent  payable by Tenant
            during the lat full month of the term, together with additional rent
            and other charges as provided herein.  The provision of this Article
            do not  exclude  Landlord  rights of  re-entry  or any  other  right
            hereunder."

            "43.  RIGHT OF FIRST OFFER:
                  --------------------

                  A. So long as: (I) Tenant is not in default  under this Lease;
            (ii) this Lease is in full force and  effect;  and (iii)  Tenant and
            any parent,  subsidiary  or  affiliate  of Tenant is  occupying  the
            entire  Premises for the purpose of conducting  its  business,  then
            Landlord  agrees that,  in the event any space in Elmwood  Corporate
            Park which is then owned by Landlord  (hereinafter called the "Offer
            Space"),  shall  become  "available  for  leasing"  (as  hereinafter
            define),  at any time and from time to time  after the  commencement
            date of this Lease, before offering to lease such Offer Space to any
            third party,  Landlord  will first offer to Tenant in writing  (such
            offer by Landlord to Tenant  being  hereinafter  called  "Landlord's
            Offer") the right to include such Offer Space within the Premises as
            of the date specified by Landlord in Landlord's  Offer  (hereinafter
            called the "Availability  Date"). The Availability Date shall be the
            date that the Offer Space which is the subject of  Landlord's  offer
            is reasonably  expected to become  available  for leasing.  Landlord
            shall specify in Landlord's  Offer,  the terms and  conditions  upon
            which  Landlord  is  willing  to lease  such  Offer  Space to Tenant
            (hereinafter  collectively  called "Landlord's  Terms"),  including,
            without limitation:

                        (1)   the Availability Date of such
            Offer Space;


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                        (2)   the amount of square footage
            contained in such Offer Space;

                        (3)   Tenant's Proportionate Share;

                        (4)   the amount of Basic Rent and
            additional rent;

                        (5)   the term of the leasing of such
            Offer Space which may be for period longer
            than the Term);

                        (6)   the location and configuration
            of such Offer Space; and

                        (7) such other terms and conditions  upon which Landlord
            is willing to lease the Offer Space to Tenant.

                  B. Tenant shall have the right to accept Landlord's Offer with
            respect  to  such  Offer  Space  within   fifteen  (15)  days  after
            Landlord's  Offer.  Time  shall be of the  essence  with  respect to
            Tenant's acceptance of Landlord's Offer. If Tenant does not duly and
            timely accept  Landlord's Offer with respect to the Offer Space: (I)
            landlord shall be under no further obligation to Tenant with respect
            thereto,  and Landlord  may then lease the Offer Space  contained in
            Landlord's  Offer (or any part or parts thereof) to others,  on such
            terms  and  conditions  (including  rent  and  additional  rent)  as
            Landlord then elects in its sole discretion.

                  C.    if Tenant duly and timely accepts
            Landlord's Offer, such Offer Space shall be
            added to the Premises on Landlord's Terms, and
            upon the following further terms and
            conditions, effective as of the Availability
            Date:

                        (1) Landlord  shall have no obligation to do any work or
            perform any services  with respect to the Offer Space,  which Tenant
            agrees to accept in its then "as is" condition;

                        (2)   the Premises shall be the space
            originally demised by this Lease, plus the
            Offer Space; and

                        (3) any other  changes which are required to reflect the
            addition  of such Offer Space  shall be  appropriately  made to this
            Lease.

                  D.    Except as expressly set forth
            hereinabove, the leasing of such Offer Space

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            shall be subject to and in  accordance  with all of the other terms,
            covenants and provisions of this Lease.

                  E. Notwithstanding the foregoing, the Offer Space shall not be
            "available  for  leasing,"  if: (I) the Offer  Space is subject to a
            right or option or a renewal right or option  contained in any other
            lease  entered into by Landlord  prior to the date hereof;  or (ii))
            the Offers  Space  remains  occupied by the tenant to whom the Offer
            Space is  presently  leased  (whether  by  renewal or  extension  or
            otherwise), or is offered for re-letting to a subtenant or assignees
            of such present  tenant;  or (iii) if another party desires to lease
            more  space in  Elmwood  Corporate  Park than  Tenant,  which  space
            includes the Offer space.

                  F.    The right of first offer set forth
            in this Article, is personal to Tenant named
            herein and may not be assigned or transferred.

                  G. Upon request of Landlord,  Tenant shall execute and deliver
            an agreement  setting forth the terms and condition sunder which any
            such Offer Space is added to the premises;  it being  understood and
            agreed  that  such  terms  and  conditions  shall   nevertheless  be
            effective   regardless  if  such   agreement  is  not  executed  and
            delivered.

                  H.  Tenant  acknowledges  and agrees  that  landlord  shall be
            obligated  to make  Landlord's  Offer to Tenant only at such time as
            each Offer Space initially becomes "available for leasing;" it being
            understood and agreed by Tenant,  the right of first offer contained
            herein is a one 91) time  right  only  with  respect  to each  Offer
            Space."

            "44.  TENANT'S RIGHT OF SELF-HELP:
                  ---------------------------

                  A. If  Landlord  fails  to make  any  repairs  or do any  work
            required  of  Landlord  solely  with  respect  to  the  roof  of the
            Building,  in accordance  with the  provisions of this Leae, and any
            such  failure  continues  for period of five 95) days  after  notice
            thereof is given by Tenant to Landlord,  or, if such failure require
            more than ten (10) days to cure in the  exercise  of due  diligence,
            unless  Landlord  commences  to cure same  within  said ten (10) day
            period an d thereafter  diligently prosecute the same to completion,
            then Tenant, in addition to such other rights and remedies as may be
            available to Tenant  hereunder,  may, but shall not be obligated to,
            make such repairs or perform such work in accordance

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            with the provision of this Lease, at Tenants
            sole cost and expense.

                  B. In the event  Tenant  makes such  repairs or performs  such
            work, Tenant shall use only those  contractors  utilized by Landlord
            in the Building for such work unless such  contractors are unwilling
            or unable to perform  such work,  in which event  Tenant may utilize
            the services of any other  qualified  contractor  which normally and
            regularly  performs  similar  work  in  comparable  building  in the
            vicinity of the Building, and provided that: (I) any such contractor
            does not void or limit any warranty or guaranty procured by Landlord
            regarding  the  roof;  (ii)  such  work is  performed  by  Tenant in
            accordance  with the  provision  of this  Leae;  and  (iii))  Tenant
            indemnifies and holds Landlord harmless from and against any and all
            claims,  damages and losses  incurred  by  Landlord  an/or any other
            tenant or occupant in the Building as a result of the making of such
            repairs or the performance of such work."

            C.    The address "90 West Franklin Street, Hackensack,
new Jersey, 07601" contained in Article 28 of the lease, shall be
deemed to be deleted, and the address "c/o Alfred Sanzari
Enterprises, P.O. Box 2187, South Hackensack, New Jersey 07606-
2187, with a copy to Cole, Schotz, Meisel, Forman and Leonard,
P.A., Court Plaza North, 25 Main Street, P.O. Box 800, Hackensack,
New Jersey 07602-0800, Attention: Edward M. Schotz, Esq." inserted
in its place.
            D. The  following  shall be  deemed to be  inserted  after the third
sentence  in Article  12 of the  Lease;  "In the event  Landlord  withholds  its
consent to the subletting or assignment as provided herein, Landlord agrees that
it will so notify  Tenant in writing  within the  aforesaid ten (10) day period,
specifying  therein,  in reasonable detail, the reason(s) for the withholding of
such consent."
      6.    A.    Tenant understands and agrees that: (I) the remises
contiguous to the Original Premises, consisting of approximately

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<PAGE>



thirty-one  thousand seven hundred  forty-four  (31,74) square feet (hereinafter
referred to as the "Contiguous  Space"), is currently leased to, and occupied by
CTX Termination, inc. (hereinafter referred to as "CTX"); and (ii) CTX exercised
its  option to renew the term of its lease  which  now  expires  March 21,  2004
(hereinafter referred to as the "CTX Lease").
            B. So long as (I)  Tenant  is not in  default  under the  Lease,  as
modified by this Amendment; (ii) the Lease, as modified by this Amendment, is in
full force and effect; and (iii) Tenant is occupying the entire Premises for the
purpose of conducing its business,  then,  provided Tenant, at its sole cost and
expense,  secures  the early  termination  of the CTX Lease,  or CTX vacates the
Contiguous  Space or the CTX Lease is terminated  prior to the expiration of the
term  thereof,  landlord  shall  give  Tenant  the  right to  relocate  from the
Additional  Space to the  Contiguous  Space,  upon not less than six (6) months'
prior written  notice given at any time prior to February 29, 2000  (hereinafter
referred to as the "Relocation Notice").

            C. In the  event  Tenant  duly  and  timely  exercise  the  right to
relocate as provided  herein,  the Contiguous Space shall be substituted for the
Additional  Space as of the effective date of such  relocation,  upon all of the
terms, covenants, conditions,  provisions and agreements contained in the Lease,
as modified by this Amendment, except that:

                  (1) "Basic  Rent" (on a per square  foot per annum  basis) and
additional  rent  shall be deemed to be the  amounts  then  payable to Tenant to
Landlord with respect to the Original Premises;

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<PAGE>



                  (2)   "Proportionate Share" shall be deemed to be
"one hundred (100%) percent";
                  (3) The number of parking  spaces  provided in  Paragraph 4 of
the Third  Amendment to Lease dated as of February 28, 1994,  shall be deemed to
be "thirty-six (36)";
                  (4)   The reference to "Adjacent Building" shall be
deemed to be deleted;
                  (5) At the time Landlord  receives the  Relocation  Notice and
upon the effective date of such relocation, Tenant shall not be in default under
this Lease;
                  (6)  Tenant  pays  to   Landlord,   simultaneously   with  the
Relocation  Notice,  a sum equal to four (4) months'  Basic Rent and  additional
rent then  payable by Tenant to  landlord  under the Lease,  as modified by this
Amendment,  as consideration  fro Tenant's  exercise of its right to relocate to
the Contiguous Space;
                  (7)  Tenant  provides   Landlord,   simultaneously   with  the
Relocation Notice, any documents which evidence the early termination of the CTX
Lease, if applicable; and
                  (8) Tenant shall be liable and  responsible  for restoring the
Contiguous Space to the condition which existed as of the effective date of such
relocation.
            D. In the event  Tenant does not duly and timely  exercise the right
to relocate as provided  herein,  the provisions of this Paragraph shall be null
and void and of no  further  force or effect  and  Tenant  shall have no further
right to relocate to the Contiguous Space.

            E. The right to relocate as provided  herein,  is personal to Tenant
named herein and may not be assigned or transferred.


                                      16

<PAGE>



            F. Upon  request of Landlord,  Tenant  shall  execute and deliver an
agreement  setting  forth the terms and  conditions  under which the  Contiguous
Space is substituted for the Additional  Space;  it being  understood and agreed
that such terms and conditions  shall  nevertheless  be effective  regardless if
such agreement is not executed and delivered.

      7.  Notwithstanding  anything to the contrary  contained herein,  Landlord
hereby approves the following work which may be performed by Tenant, at its sole
cost and expense,  subject  nevertheless  to all of the other terms,  covenants,
conditions,  provisions  and  agreements  of the  Lease,  as  modified  by  this
Amendment (including, without limitation, article 22 thereof):

            A. the conversion of approximately five thousand (5,000) square feet
of warehouse  space currently  existing in the Original  Premises as of the date
hereof, to space to be utilized for production; and

            B. the conversion of approximately  eleven thousand  (11,000) square
feet of warehouse  space currently  existing gin the Additional  Space as of the
dat hereof, to office space.

      8. Tenant  hereby  affirms that  security in the amount of One Hundred Two
thousand four Hundred Sixty-Two and 72/100 ($102,462.72)  Dollars has heretofore
been deposited by Tenant to Landlord under the lease.
      9. Tenant hereby represents and warrants to Landlord,  that Tenant has not
dealt with any real estate  agent or broker in  connection  with this  Amendment
and/or the  Additional  Space,  that this  Amendment  was not  brought  about or
procured through the use or instrumentality of any agent or broker, and that all
negotiations with respect to the term of this Amendment were conducted between

                                      17

<PAGE>



landlord,  and Tenant.  Tenant hereby covenants and agrees to indemnify and hold
Landlord  harmless from and against any and all claims for commissions and other
compensation  made by any agent or agents  and/or any broker or brokers based on
any dealings  between  Tenant and any agent or agents  and/or broker or brokers,
together  with all costs and  expenses  incurred by Landlord in  resisting  such
claim s(including, without limitation, attorney's fees and disbursements).

      10. A. Except as expressly  modified by this Amendment,  the Lease and all
the terms, covenants, conditions,  provisions and agreements thereof, are hereby
in all respects, ratified, confirmed and approved.

            B. Tenant hereby  affirms that, as of the date hereof,  no breach or
default  by  Landlord  has  occurred,  and that the Lease and all of its  terms,
covenants,  conditions,  provisions and  agreements,  except as modified by this
Amendment, are in full force and effect, with no defenses or offsets thereto.

            C. Tenant  hereby  releases  Landlord  of and from all  liabilities,
claims  controversies,  causes of action an other matters of every nature which,
through  the date  hereof,  have or might  have  arisen  out of or in any way in
connection with the Lease and/or the Demised Premises.
      11. This Amendment and the Lease contain the entire understanding  between
the parties with respect to the matters contained  herein.  No  representations,
warranties,  covenants or agreements  have been made concerning or affecting the
subject matter of this amendment, except as are expressly contained herein.
      12. This Amendment may not be changed orally,  but only by an agreement in
writing  by  the  party  against  whom   enforcement  of  any  waiver,   change,
modification or discharge is sought.

                                      18

<PAGE>



      13. This  Amendment  shall be binding upon, an enure to the benefit of the
parties hereto, their respective legal representatives,  successors, and, except
as  otherwise  provided  I the  Lease,  as  modified  by  his  amendment,  their
respective assigns.
      14. The  submission of this  Amendment to Tenant shall not be construed as
an offer, nor shall Tenant have any rights with respect hereto, unless and until
Landlord shall execute a copy of this Amendment an  unconditionally  deliver the
same to Tenant.
      15.  Tenant  hereby  represents  and  warrants to landlord  that:  (I) the
execution, performance and delivery by Tenant of this Amendment does not violate
any  provisions  of its  Charter  or By- Laws,  and has been  fully and  validly
authorized  and approved by any required  corporate  action of Tenant;  (ii) the
obligations  of Tenant  under this  Amendment  are  legal,  valid,  binding  and
enforceable  against Tenant in accordance with its terms;  and (iii)) the person
executing  this  Amendment has the authority to so execute,  perform and deliver
this Amendment on behalf of Tenant.
      16.  Tenant  hereby  acknowledges  and agrees that this  Amendment  is the
result of extensive  negotiations  between the parties.  This Amendment shall be
construed without regard to any presumption or other rule requiring construction
against the party causing this Amendment to be drafted or prepared.
      17.  A  determination  that  any  provision  of  this  Amendment  is  void
unenforceable or invalid shall not affect the  enforceability of validity of any
other provision,  and any determination that the application of any provision of
this  Amendment  to any  person or to  particular  circumstance  sis  illegal or
unenforceable  shall not affect the enforceability or validity of such provision
as it may apply to other person or circumstances.

                                      19

<PAGE>



      18. This  Amendment may be executed in one or more  counterparts,  each of
which,  when so executed and  delivered,  shall be deemed  original,  but all of
which taken together shall constitute but one and the same instrument.
      19. The validity,  performance  and enforcement of this Amendment shall be
governed  by and  construed  in  accordance  with the  laws of the  State of new
Jersey.
      IN WITNESS  WHEREOF,  the parties hereto have  respectively  executed this
Fourth Amendment to Lease as of the day and year first written above.

Witness for Landlord:                     ALFRED SANZARI ENTERPRISES,
                                          L.P.

                                          By:   Alfred Sanzari
                                                Enterprises, Inc., its
                                                General Partner


                                          By:
-------------------------------
                                          Name: David Sanzari
                                          Title: President

Attest for Tenant:                        BIO-REFERENCE LABORATORIES,
                                          INC.

By:                                       By:
   ----------------------------
Name:                                     Name:
      ------------------------
Title:              Secretary             Title:              President
       -------------                             -------------

                                      20