Document:

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                                                                   EXHIBIT 10.25

LUCLIFF COMPANY LIMITED
Commercial & Residential Development
LuCliff Place                                               Tel : (416) 595-1774
700 Bay Street, Toronto, Ontario Canada M5G 1Z6             Fax : (416) 595-1745
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                                          November 30, 2000

Visible Genetics Inc.
Suite 1000
700 Bay Street
Toronto, Ontario
M5G 1Z6

Attention:  Mr. Drasko Puseljic

Dear Sirs:

            Re:   LuCliff Company Limited (the "Landlord")
                  lease to Visible Genetics Inc. (the "Tenant")
                  9th - 12th Floors, 700 Bay Street, Toronto
                  Date of Lease: March 27, 2000
                  (the "Lease")
                  OUR FILE NUMBER: R240.97

            Further to our recent telephone conversations we confirm that
LuCliff Company Limited has agreed with Visible Genetics Inc. to extend the 9th
Floor Term and to modify the provisions of Section 19.01 of the Lease relating
to the Tenant's option to extend the 9th Floor Term on the terms and conditions
set out below:

1.    The 9th Floor Term is extended for a further period of six (6) months from
      June 1, 2001, to November 30, 2001, subject to the Tenant's right to
      terminate the Lease of the 9th Floor portion of the Leased Premises
      described in paragraph 3 below.

2.    Section 19.01(a) of the Lease is amended to provide that:

      (a)   the date for delivery of notice in writing exercising the Tenant's
            first option to extend the 9th Floor Term shall be postponed from
            November 30, 2000, to May 31, 2001;

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Visible Genetics Inc.
November 30, 2000
Page 2

      (b)   the option to extend the 9th Floor Term shall not be for a period of
            one year but shall be for a period of six months commencing December
            1, 2001, and expiring on May 31, 2002; and

      (c)   if the Tenant does not deliver the notice as aforesaid on or before
            May 31, 2001, the 9th Floor Term shall expire on November 30, 2001,
            subject to the Tenant's right to terminate the Lease of the 9th
            Floor portion of the Leased Premises as described in paragraph 3
            below.

3.    The Tenant shall have the right to terminate the Lease of the 9th Floor
      portion of the Leased Premises prior to its extended expiry date of
      November 30, 2001, by delivery of not less than six (6) months notice to
      the Landlord, and in such case the 9th Floor Term shall expire on the date
      set out in such notice. For greater clarity the parties acknowledge and
      agree that:

      (a)   the date of expiration of the 9th Floor Term set out in the Tenant's
            notice of termination may not be later than November 30, 2001, nor
            earlier than the date that is six (6) months following the delivery
            of the notice;

      (b)   the Tenant's right to terminate the Lease of the 9th Floor portion
            of the Leased Premises shall expire on May 31, 2001, and shall not
            apply during any further extension of the 9th Floor Term pursuant to
            Section 19.01, during any renewal term of the Lease pursuant to
            Section 19.02 of the Lease, or during any further or other extension
            or renewal of the Lease Term.

4.    The extension of the 9th Floor Term described in paragraph 1 above shall
      be upon the same terms and conditions as described in Section 19.01(a) of
      the Lease with respect to the extension of the 9th Floor Term pursuant to
      the option therein contained, save and except that:

            (a) if the Tenant does not exercise its option to extend the 9th
            Floor Term under Section 19.01(a) of the Lease (as amended by
            paragraph 2 above), or if the Tenant delivers notice of termination
            pursuant to paragraph 3 above, then the Basic 9th Floor Rent during
            such term extension (i.e. for the period from and after May 31,
            2001) shall not be market rental as set out in the said Section
            19.01(a) but shall be TWELVE DOLLARS ($12.00) multiplied by the
            number of square feet of Rentable Floor Area of the 9th Floor
            portion of the Leased Premises; and

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Visible Genetics Inc.
November 30, 2000
Page 3

            (b) if the Tenant does exercise its option to extend the 9th Floor
            Term under Section 19.01(a) of the Lease (as hereby amended), the
            Basic 9th Floor Rent shall be determined in accordance with the
            provisions of Section 19.01(a) of the Lease, and will be the same
            for the six month extension period described in paragraph 1 above
            and for the further six month extension pursuant to the option.

5.    Except as expressly modified and amended by this letter all of the terms,
      conditions, covenants, and provisos of the Lease shall remain in full
      force and effect. Terms and expressions when used in this letter shall
      have the same meaning as when used in the Lease unless the context
      otherwise requires.

            Please sign a copy of this letter where indicated below to confirm
your agreement to the above Lease amendments.

                                          Yours truly,

                                          LUCLIFF COMPANY LIMITED

JF:dmm                                    Per:
                                                Joseph Fong, General Manager

            We hereby agree that the above letter sets out our agreement with
respect to amendments to the above Lease.

            DATED at Toronto, this       day of December, 2000.

                                          VISIBLE GENETICS INC.

                                          Per:
                                                Thomas J. Clarke, C.F.O.<PAGE>

                                                                   EXHIBIT 10.26

            THIS LEASE made as of the first day of October, 2000.

                  B E T W E E N:

                  LUCLIFF COMPANY LIMITED

                  (hereinafter referred to as the "Landlord")

                                        OF THE FIRST PART

                  - and -

                  VISIBLE GENETICS INC., a Corporation
                  duly incorporated under the laws of the
                  Province of Ontario

                  (hereinafter referred to as the "Tenant")

                                        OF THE SECOND PART

            WHEREAS by a Lease dated the 27th day of March, 2000, (the "Existing
Lease") the Landlord leased to the Tenant certain premises being approximately
twenty seven thousand, five hundred and four (27,504) square feet on the 9th,
10th, 11th, and 12th floors of the office building known as 700 Bay Street,
Toronto, and more particularly described therein, on the terms and conditions
therein set forth.

            AND WHEREAS the Tenant wishes to lease additional premises on the
14th floor of the Building adjacent to the premises leased pursuant to the
Existing Lease upon the terms and conditions hereinafter set forth.

DEMISE AND TERM

1.          In consideration of the rents, covenants, and agreements herein
contained on the part of the Tenant to be paid, observed and performed, the
Landlord hereby leases to the Tenant and the Tenant leases from the Landlord,
the entire 14th floor of the Office Section comprising approximately six
thousand, eight hundred and seventy six (6,876) square feet of Rentable Floor
Area, and more particularly described as outlined in red on the plan of the 14th
floor attached hereto as Schedule "A" to this lease for and during the term of
FOUR (4) YEARS, SIX (6) MONTHS, AND FIFTEEN (15) DAYS to be computed from the
15th day of November, 2000, and from thenceforth next ensuing and fully to be
completed on the 31st day of May, 2005;

BASIC RENT

2.    (a)   The Tenant shall pay yearly and every year during the Term without
any deduction, abatement, set-off, or diminution whatsoever, a Basic Rent of
EIGHTY TWO THOUSAND, FIVE HUNDRED AND TWELVE DOLLARS ($82,512.00) of lawful
money of Canada, payable in equal consecutive monthly instalments in advance of
SIX THOUSAND, EIGHT HUNDRED AND SEVENTY SIX DOLLARS ($6,876.00) upon the date of
commencement of the Term and on the first day of each and every calendar month
during the Term thereafter, such payments to be made by cheque or money order
payable to the Landlord, or as it may direct in writing from time to time, and
to be payable at 700 Bay Street, Toronto, Ontario M5G 1Z6, or at such other such
place as the Landlord may direct in writing from time to time.

      (b) It is acknowledged and agreed that the rent described in this
paragraph 2 is based on an annual rental of TWELVE DOLLARS ($12.00) per square
foot of Rentable Floor Area of the Leased Premises. It is further acknowledged
and agreed that the Landlord's architect has certified

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                                   Page - 2 -

that the Leased Premises has a Rentable Floor Area of six thousand, eight
hundred and seventy six (6,876) square feet, and the Tenant acknowledges and
agrees that it is satisfied with the said Landlord's architect's certificate.

ADDITIONAL RENT

3.    The Tenant shall also pay to the Landlord yearly and every year during the
Term, Additional Rent as described in the Existing Lease; Without limiting the
generality of the foregoing the Tenant shall pay to the Landlord Taxes as
described in Article 6 of the Existing Lease and the Tenant's Proportionate
Share of Operating Costs as described in Article 5 of the Existing Lease.

LANDLORD'S WORK, EARLY OCCUPANCY

4.          The Landlord agrees to do the following work as soon as reasonably
possible following execution of this Lease and will use its reasonable efforts
to complete such work on or before the 15th day of October, 2000:

      (a)   demolish and remove all existing leasehold improvements throughout
      the Leased Premises including all interior partition walls and floor
      coverings;

      (b)   refurbish the washrooms and the elevator lobby in the Leased
      Premises to the same standard as the work done on the 9th - 12th floors of
      the Office Section;

      (c)   install new Building standard ceiling tiles and lighting throughout
      the Leased Premises.

            It is agreed that the foregoing work shall constitute the Landlord's
base building work and will not form part of the cost of the Tenant's leasehold
improvements described in paragraph 6 below.

            If the Landlord has not substantially completed the work described
in subparagraphs (a) and (c) above by October 15, 2000, then the commencement
date of the Term shall not be postponed but the Tenant shall not be required to
pay any Basic Rent or Additional Rent until the date that is thirty (30) days
after the Landlord has substantially completed such work; provided that the
Tenant shall be required to pay for any Additional Services and for utilities
consumed in the Leased Premises during such period.

5.          As soon as the Landlord's Work described in subparagraphs 4 (a) and
(c) above is substantially completed, the Tenant shall be entitled to occupy the
Leased Premises prior to the commencement date of the Term, but upon not less
than one (1) business day's written notice to the Landlord, for the purposes of
constructing its leasehold improvements, including installation of its trade
fixtures, furniture, equipment, and telephone and computer cabling. The Tenant
shall be bound by all of the terms, conditions, covenants, and provisos of this
Lease during any period of occupation prior to the commencement date of the
Term, save and except that during such period or periods the Tenant shall not be
required to pay any Basic Rent or Additional Rent whether or not the Tenant
carries on business in the Leased Premises; provided that the Tenant shall be
required to pay for any Additional Services and for utilities consumed in the
Leased Premises during any such period of early occupancy.

TENANT'S LEASEHOLD IMPROVEMENTS ALLOWANCE

6.          Provided that this Lease has been fully executed by the Landlord and
the Tenant the Landlord shall pay to the Tenant a leasehold improvement
allowance (the "Allowance") of up to TWENTY DOLLARS ($20.00) per square foot of
Rentable Floor Area of the Leased Premises; The Allowance will be paid on a
monthly basis as the costs are incurred as evidenced by invoices related to
Tenant improvements work on the Leased Premises delivered to the Landlord by the
Tenant up to the maximum of TWENTY DOLLARS ($20.00) per square foot as
aforesaid. The construction of the Tenant's leasehold improvements shall be
governed by the provisions of Section 7.16 of the

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                                   Page - 3 -

Existing Lease.

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                                   Page - 4 -

OPTION TO RENEW

    7. If the Tenant has exercised the option to renew described in Section
19.02 of the Existing Lease and provided that the Tenant has reasonably abided
by all the terms, conditions, and covenants of this Lease, including the
covenant to pay rent, is not then in default of any such term, condition, or
covenant beyond any applicable notice and cure periods, and has not become
insolvent or bankrupt or had a receiver appointed in respect of its assets or
business the Tenant shall have the option to renew this Lease for one further
term of five (5) years; Provided that in order to exercise its option to renew
the Tenant shall be required to give the Landlord notice thereof in writing not
later than November 30, 2004, and not earlier than June 1, 2004. If the Tenant
does not deliver the notice as aforesaid, this Lease shall terminate upon the
expiration of the Term on May 31, 2005. Any renewal pursuant to this paragraph 7
shall be upon the same terms, conditions, and covenants contained in this Lease,
except that:

      (a)   there shall be no further right to renew this Lease;

      (b)   the Basic Rent payable pursuant to paragraph 2 of this Lease shall
      not apply, but the Basic Rent for such renewal term shall be the market
      rental per square foot for similar improved premises in the Building and
      any other buildings of comparable quality, size, age, and location as the
      Building at the commencement of the renewal term multiplied by the number
      of square feet of Rentable Floor Area of the Leased Premises. If the
      Landlord and the Tenant have not agreed upon such said current market
      rental prior to sixty (60) days before the expiry of the Term the issue
      shall NOT be referred to arbitration, but this option to renew shall be
      null and void and the Term shall expire on May 31, 2005;

      (c)   Sections 19.03, 19.04 and 19.05 of the Existing Lease shall not
      apply and paragraphs 4, 5, and 6 of this Lease shall not apply;

      (d)   for greater clarity the Leased Premises shall be leased on an "as
      is" basis, the Landlord shall not be required to do any work in connection
      therewith, including any of the work described in Section 19.04 of the
      Existing Lease or paragraph 4 above, and there shall be no rent free
      period, fixturing period, leasehold improvement allowance, or other tenant
      inducement payments or allowances.

INCORPORATION OF TERMS AND
CONDITIONS OF EXISTING LEASE

8.    (a)   The Landlord and the Tenant covenant and agree that except as
otherwise provided for in this Lease, the terms, conditions, covenants, and
provisos contained the Existing Lease shall be incorporated into and shall form
part of this Lease, and the Landlord and the Tenant shall be bound by and shall
observe and perform all of the terms, conditions, covenants, and agreements on
their parts respectively to be performed or observed thereunder. For greater
clarity the provisions of Article 3 of the Existing Lease (Demise and Term) and
Section 4.01 (Basic Rent) shall not apply to this Lease and the provisions of
paragraph 1, 2, and 4 shall apply in their place and stead.

      (b)   Notwithstanding the provisions of subparagraph (a) above the
following sections of the Existing Lease shall not apply to and shall not form
part of this Lease:

            (i)   Section 19.01 regarding the Tenant's Option to Extend the 9th
            Floor Term;

            (ii)  Section 19.02 regarding an Option to Renew; The Tenant's
            Option to renew this Lease shall be as set out in paragraph 7 of
            this Lease;

            (iii) Section 19.03 regarding the Tenant's Leasehold Improvements
            (Tenant's Allowance;

            (iv)  Section 19.09 regarding Parking;

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                                   Page - 5 -

            (v)   Section  19.10  regarding  Tenant's  Right of first  Offer
            with respect to the 14th floor;

            (vi)  Section 19.11 regarding Commission.

      (c)   All terms and expressions defined in the Existing Lease shall have
the same meanings when used in this lease as when used in the Existing Lease
unless the context otherwise requires and except that:

                  (i)   "Leased  Premises"  shall mean the  Leased  Premises
            described in paragraph 1 of this Lease;

            (ii)  "Term"  shall mean the Term  described  in  paragraph 1 of
            this Lease;

                  (iii) "Existing Lease" shall mean the Lease described in the
            first recital to this Lease and shall NOT mean the "Existing Lease"
            described in Section 3.02 of the said Existing Lease.

            IN WITNESS WHEREOF the parties of the first and second parts have
hereunto affixed their respective corporate seals, attested by the hands of
their duly authorized officers in that behalf.
                                             LUCLIFF COMPANY LIMITED

                                             Per:_______________________________
                                                   Joseph Fong, General Manager

                                             Date of signature:

                                             VISIBLE GENETICS INC.

                                             Per:_______________________________
                                                   Thomas J. Clarke,
                                                   Chief Financial Officer

                                             Date of signature:

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