Document:

<PAGE>

                           SUB-LEASE - RAD-BYNET GROUP
                                   March 1999

Concluded on March___1999 between the Company RAD Data Communications Ltd.
(hereinafter : "the Lessor") and the Company RADVision Ltd. (hereinafter : "the
Lessee"), as follows :

1.       "The Premises" - an area of 292 square metres on Level A in Stage B in
         the building situate at 24 Raoul Wallenberg Road Tel Aviv, as marked on
         the diagram in ANNEX A together with 32 parking bays.

2.       The Lessor leases the Premises under a sub-lease from the Company Bay
         Networks (Israel) Ltd. (hereinafter : "Bay") which leases the Premises
         from Vitalgo Textile Enterprises Ltd. (hereinafter : "the Owner").

3.       Bay and the Owner have given approval to the Lessor for the lease of
         the Premises to the Lessee, subject to the agreements between Bay and
         the Owner and between Bay and the Lessor (hereinafter : "the Principal
         Lease Agreements"). The Principle Lease Agreements are attached hereto
         as ANNEX C.

4.       Subject to the provisions of the Principal Lease Agreements and of this
         Agreement, the Lessee leases the Premises from the Lessor under a
         sub-lease with effect from 18th March 1999 (hereinafter : "the Date of
         Commencement of the Lease") until 30th September 2000 (hereinafter :
         "the Lease Period"). Notwithstanding all the foregoing, should this be
         required by the Owner and/or by Bay, the Lessor shall have the right to
         give notice of termination of the lease to the Lessee prior to the
         expiration of the Lease Period at such time as it shall be required so
         to do by the Owner and/or by Bay. The Lessee shall not be entitled to
         any consideration and/or compensation of any kind arising from the
         termination of the Agreement for any reason. The provisions of this
         paragraph are fundamental provisions and constitute the basis for the
         entering into of contractual arrangements under this Agreement.

         Should the Lessor also continue to lease the Premises from Bay and/or
         from the Owner after 30th September 2000, an option shall be granted to
         the Lessee to extend the Lease Period and for the lease of the Premises
         by the Lessor for the entire duration of the Lessee's further Lease
         Period from Bay and/or the Owner (hereinafter : "the Further Lease
         Period"), subject however to all the provisions of this Agreement, to
         the Principal Lease Agreements, including the amendments thereto, if
         any, and such agreements for the renewal of the lease relating to the

<PAGE>

         Premises as shall, if at all, be entered into between the Lessor and
         Bay and/or the Owner.

5.       The Lessee accepts the Premises in their present condition, "As Is", in
         clean and good condition, meeting its needs (hereinafter : "the Basic
         Condition of the Premises").

6.       Should the Lessee request alterations to be effected to the Premises in
         a departure from the Basic Condition of the Premises, the Lessor shall
         effect the same in accordance with such specification and plans as
         shall be approved in advance and in writing by the Lessor and which
         shall be attached as ANNEX B to this Agreement. Upon the termination of
         this Agreement for any reason, should the Owner and/or Bay require
         this, the Lessee shall be obliged to restore the Premises to the Basic
         Condition of the Premises. For the sake of clarity, the Lessee shall
         not be required to reinstate the former condition and to remove those
         alterations which had been made as set forth in the diagram attached to
         letter from Mr. Yehuda Kashti dated 17th March 1999, attached to this
         Agreement as ANNEX E. After the alterations have been effected, as set
         out above, the Lessee shall not effect any further alteration to the
         premises (hereinafter : "the Further Changes") without the prior
         written consent of the Lessor.

7.       The monthly rental shall be as follows :

         7.1      A sum in new Israeli shekels equal to US $ 18.5 per square
                  metre. A sum in new Israeli shekels equal to US $ 120 for each
                  covered parking bay.

                  Should during the Further Lease Period the rental which the
                  Lessor pays to Bay and/or to the Owner increase, the rental
                  payable by the Lessee to the Lessor as set forth above shall
                  be increased in the same proportion.

                  The aforesaid rental shall be translated into new Israeli
                  shekels at the representative rate of exchange of the dollar
                  as at 18th March 1999, from which date it shall be linked to
                  the Consumer Price Index as is know on the date of each and
                  every actual payment.

         7.2      In addition to the rental and to the payments set forth above,
                  the Lessee shall be responsible for the payments set forth in
                  paragraphs 9 and 10 hereunder.

<PAGE>

8.       The rental, including value added tax, shall be paid quarterly for
         three (3) months in advance, on the first day of each calendar month,
         or on the first business day next following the first day of the month
         if this day is a Sabbath or Holiday. The first payment shall be on 15th
         April 1999 for the months 18th March - to June 30 1999, and with effect
         from the second payment on the first day of the month commencing on
         each annual quarter.

9.       The Lessee shall be responsible for all the on-going payments
         associated with the use of the Premises during the Lease Period,
         including municipal assessment rates, accounts for water, electricity,
         gas, telephone (including the cost of the extensions and the
         installation thereof), maintenance and air conditioning. Debiting shall
         be effected in the manner ordinarily applied by the RAD-Bynet Group
         from time to time (as the Lessor shall determine).

10.      The Lessee undertakes to enter into a management agreement with the
         Management Company of the building in the form attached to this
         Agreement as ANNEX D, and to sign any revision or addendum thereto, and
         it shall be obliged to comply with all its obligations in accordance
         with that agreement. Failure to sign an agreement with the Management
         Company or any breach of the agreement between the Lessee and the
         Management Company shall be regarded as a breach of this Agreement on
         the part of the Lessee, and it is expressly recorded that non payment
         of the management and maintenance fee to the Lessor or to the
         Management Company as required and on the due date thereof shall be
         deemed to be a fundamental breach of this Agreement on the part of the
         Lessee. Furthermore, it is recorded that the cleaning of the interior
         of the Premises is optional and is not comprised within the services
         which the Lessee shall receive from the Lessor or from the Management
         Company.

11.      A delay of 3 or more months in any payment due by the Lessee under this
         Agreement shall constitute a fundamental breach of this Agreement by
         the Lessee and shall confer upon the Lessor the right to evict the
         Lessee forthwith. Without prejudice to the Lessor's right to evict the
         Lessee as aforesaid - this shall accord the Lessor the right to enforce
         such payment against the Lessee and inasmuch that the Lessee may have
         failed to effect such payment on due date thereof, the Lessee shall
         also be liable to pay the Lessor arrears interest on the amount so in
         arrears at the Libor rate applicable at such time plus 3% per month to
         date of actual payment. The receipt of the interest by the Lessor shall
         be in addition to its rights under this Agreement and under any law and
         the receipt thereof shall not be and shall not be considered as a
         waiver of any rights accorded to it in pursuance of this Agreement or
         under any law.

<PAGE>

12.      Upon the expiration of the Lease Period or termination thereof as
         defined in paragraph 2 above, as the case may be, the Lessee undertakes
         to restore the Premises and the appurtenances therein to the same
         condition as they had been received after effecting the alterations to
         the Basic Condition of the Premises and prior to carrying out any
         Further Alterations (if any), including re-painting and cleaning as set
         forth in paragraph 3 above, save for normal wear and tear resulting
         from ordinary and reasonable use or deterioration caused to the
         Premises during the Lease Period, notwithstanding ordinary and
         reasonable use by the Lessee or by a person on its behalf or under its
         authority, or as a result of VIS MAJOR.

13.      The Lessee shall be liable for damage caused as a result of the lease
         and the use of the Premises by it and/or by its agents and/or by its
         invitees and/or any person on its behalf. The Lessee shall repair any
         damage as aforesaid in accordance with the Lessor's requirements.

14.      The Lessee is an insured within the framework of the insurance held by
         the RAD-Bynet Group and shall remain such an insured for the entire
         Lease Period as shall be customarily applied by the Group from time to
         time.

15.      The Lessee shall not be entitled to transfer any part of its rights in
         and to the Premises.

16.      Should the level of the holdings of Yehuda Zisapel and Zohar Zisapel
         decline, directly or indirectly below 25% of the issued share capital
         of the Lessee, and this as a guarantee for the fulfilment of all the
         obligations of the Lessee under this Agreement, the Lessee shall
         deposit with the Lessor, immediately upon receipt of the Lessor's
         initial request, and to its order, an autonomous unconditional,
         transferable bank guarantee, capable of foreclosure in its entirely or
         in stages at any time without attributing any reason therefor; in an
         amount in new Israeli shekels equal to 6 months rental, including
         management fees, calculated at the rate applicable at the time of the
         issue of such bank guarantee. The guarantee shall be linked to the
         Consumer Price Index. The guarantee shall be valid for the entire Lease
         Period then remaining at the time of receipt of the Lessor's initial
         request, plus 3 months, and the validity thereof shall be renewed from
         time to time, one month prior to the date on which such validity is due
         to lapse, up to the expiration of the Option Period plus 3 months after
         the expiration of such Option Period. The guarantee shall be duly
         stamped and all costs involved in the issue thereof shall be due solely
         be the Lessee.

<PAGE>

17.      Remarks :

         ---------------------------------------------------------
         ---------------------------------------------------------
         ---------------------------------------------------------

                 RAD                                     RADVISION LTD.

      --------------------------------                   ------------------
      RAD Data Communications Ltd.                       RADVision Ltd.

<PAGE>

                                    ANNEX A

[This Exhibit consists of a two dimensional floor plan for the leased
premises (an area of 292 square meters on Level A in Stage B, together with
32 parking bays) at 24 Raoul Wallenberg Street Tel Aviv Israel. The floor
plan shows a cross sectional view of room divisions within the premises.]

<PAGE>

                                   ANNEX B

Works to be performed at the leased premises at 24 Raoul Walenberg Street Tel
Aviv Israel--

                                     [NONE]

<PAGE>

                                     ANNEX C

1) Summary of lease agreement between Bay Networks (Israel ) 1996 Ltd. and
Vitalgo Textile Industries Ltd. - translated from Hebrew original

<TABLE>
<S>               <C>

Date of Lease:    June 11, 1996

Landlord:         Vitalgo Textile Industries Ltd.

Tenant:           Bay Networks (Israel) 1996 Ltd..

Premises:         24 Raoul Wallenberg Street, Tel Aviv Israel.

Square Meters:    2112 sq meters and 76 parking spaces.

Permitted Use:    Industry and data communications.

Term:             2 initial years and option to extend the lease to additional
                  3 years, (each extension one year )

                  (a) Scheduled commencement date: October 6, 1996.
                  (b) Scheduled expiration date:   October 5, 1998.

Security Deposit:          $132,000 in bank guarantee.
</TABLE>

2) Summary of lease agreement between Bay Networks Ltd. and RAD Data
Communications Ltd, - translated from Hebrew original

<TABLE>
<S>               <C>

Date of Lease:    March 10, 1999

Landlord:         Bay Networks (Israel) 1996 Ltd.

Tenant:           RAD Data Communications Ltd...

Premises:         24 Raoul Wallenberg Street, Tel Aviv Israel.

Square Meters:    1056 sq meters and 32 parking spaces.

Permitted Use:    development, marketing and manufacturing of data
                  communications products.

Term:             18.5 months.

                  (a) Scheduled commencement date: March 18, 1999
                  (b) Scheduled expiration date:   September 30, 2000.
</TABLE>

Rent - $18.50 per square meter, i.e. $19,536 per month. and $120 per parking
space, i.e. $3840.

Security Deposit:          $61,000 in bank guarantee.

<PAGE>

                                     ANNEX D

           Summary of Management Agreement--translated from Hebrew original

Management Company:   Ariel Properties--ZIV towers Management Ltd.

Building-  24 Raoul Wallenberg Street Tel Aviv Israel.

Services:  Providing maintenance services to the shared area in the building.

Fees:      Each tenant will pay the pro rata of its share in the shared areas,
           according to actual costs paid by the management company plus 10%
           (provided such costs are reasonable and as customary in similar
           buildings). Such fees will be paid quarterly.

<PAGE>

                                   ANNEX E

Summary of letter from Landlord addressed to the Registrant - translated from
Hebrew original

         After performing the changes as detailed in the two dimensional floor
plan attached to the landlord's letter, Registrant will not be required to
restore the premises to their previous condition.<PAGE>
                                                                   Exhibit 10.8

                                 LEASE AGREEMENT

Concluded on 31st December 1997 between the companies Zisapel Properties (1992)
Ltd. and Klil & Michael Properties (1992) Ltd. (hereinafter : "the Lessor"), and
the company RADVision (hereinafter : "the Lessee") herein represented by
__________ .

1.       "The Premises" - an area of 880 square metres on level B , ___ square
         metres on the ___ level and ___ square metres on the ___ basement level
         of the building situate at 24 Raoul Wallenberg Street, Tel Aviv, as
         marked on the diagram in ANNEX A together with 21 covered parking bays
         and ___ open parking bays.

2.       The Lessee leases the Premises from the Lessor with effect from 15th
         January 1998 (hereinafter : "the Date of Commencement of the Lease")
         until 31st December 1998 (hereinafter : "the Initial Lease Period").
         The Lessee shall have an option to extend the lease until 31st December
         1999, thereafter until and ___ and thereafter until and ___ (each of
         the above periods of extension shall hereunder be called : "the Option
         Period", the Initial Lease Period and each of the Option Periods may
         also hereunder sometimes be called "the Lease Period"). The Lessor
         shall give 60 days prior written notice to the Lessee as to the
         exercise of the Option. During the Option Periods all the conditions of
         this Agreement shall, MUTATIS MUTANDIS, apply. Notwithstanding the
         foregoing provisions, the Lessee shall be entitled to terminate the
         Lease Period prior to the expiration of the Lease Period or any Option
         Period, if a substitute lessee is found from within the RAD-Bynet Group
         and upon 90 days prior written notice. Notwithstanding the foregoing,
         the Lessor shall have the right to give notice to the Lessee as to the
         termination of the lease at any time and for any reason, upon 90 days
         prior written notice. In any event the inclusive Lease Periods shall
         not exceed nine years and eleven months.

3.       The Lessee accepts the Premises in clean and good condition, meeting
         its needs, including air conditioning, kitchenette, toilets, on a
         marble, ceramic, granite, porcelain floor, gypsum partitioning,
         acoustic ceilings, PVC carpets, ___ standard telephone extensions, ___
         parallel telephone extensions, ___ smart telephone extensions and ___
         speakers (hereinafter : "the Basic Condition of the Premises").

4.       Should the Lessee request that alterations be effected to the Premises
         in a departure from the Basic Condition of the Premises, the Lessor
         shall effect the same as set forth in ANNEX B. Should the Lessee leave
         the property prior to the expiration of 4 years from the Date of
         Commencement of the Lease, the Lessee shall refund to the Lessor the
         cost of such alterations to the Premises as set forth

<PAGE>

         in ANNEX B, together with interest at 5% per annum reckoned from the
         date on which such alterations were effected to date of actual payment.
         After effecting such alterations as set out above, the Lessee shall not
         effect any further alteration to the Premises (hereinafter : "Further
         Alterations"), without the prior written consent of the Lessor. Should
         the Lessee so effect any Further Alterations as aforesaid - the Lessee
         alone shall bear all the costs involved therein.

5.       The monthly rental shall be as follows :

         5.1      A sum in new Israeli shekels equal to US $ 16 per square
                  metre. A sum in new Israeli shekels equal to US $ 90 for each
                  covered parking bay. A sum in new Israeli shekels equal to US
                  $ 60 for each open parking bay.

                  The rental shall be paid at the representative rate of
                  exchange of the dollar as shall be known on the date of actual
                  payment, together with value added tax.

         5.2      In addition, in the first year the Lessee shall pay an amount
                  in new Israeli shekels equals to US $ _____ per month for the
                  installation of an infrastructure for computers on the
                  Premises. Such payment shall be made in conjunction with the
                  rental as set forth in paragraph 6 hereunder.

         5.3      In addition to the rental and to the payments set forth above,
                  the Lessee shall be responsible for all the amounts set forth
                  in paragraphs 7 and 8 hereunder.

6.       The rental shall be paid quarterly for three (3) months in advance on
         the first day of each calendar month, or on the first business day next
         following the first day of the month, should this day fall on a Sabbath
         or Holiday. The first payment shall be on __________ for the months of
         __________ , and with effect from the second payment, on the first day
         of the month commencing on each annual quarter.

7.       The Lessee shall be responsible for all the on-going payments
         associated with the use of the Premises during the Lease Period,
         including municipal assessment rates, accounts for water, electricity,
         gas, telephone (including the cost of the extensions and the
         installation thereof), maintenance and air conditioning. Debiting shall
         be effected in the manner ordinarily applied by the RAD-Bynet Group
         from time to time.

<PAGE>

8.       The Lessor shall provide management and maintenance services to the
         structure in which the Premises are situate, subject to and as set
         forth in the management agreement attached to this Agreement as ANNEX
         C.

         When required to do so, the Lessee undertakes to enter into an
         agreement with the Management Company for the entire Lease Period in
         such form as shall be prescribed by the Lessor from time to time, and
         to sign any revision or addendum thereto and it shall be obliged to
         comply with all its obligations in accordance with that agreement.
         Failure to sign an agreement with the Management Company or any breach
         of the agreement between the Lessee and the Management Company shall be
         regarded as a breach of this Agreement on the part of the Lessee, and
         it is expressly recorded that non payment of the management and
         maintenance fee to the Lessor or to the Management Company as required
         and on the due date thereof shall be deemed to be a fundamental breach
         of this Agreement on the part of the Lessee. Furthermore, it is
         recorded that the cleaning of the interior of the Premises is optional
         and is not comprised within the services which the Lessee shall receive
         from the Lessor or from the Management Company.

9.       A delay of 3 or more months in any payment due by the Lessee under this
         Agreement shall constitute a fundamental breach of this Agreement by
         the Lessee and shall confer upon the Lessor the right to evict the
         Lessee forthwith. Without prejudice to the Lessor's right to evict the
         Lessee as aforesaid - this shall accord to the Lessor the right to
         enforce such payment against the Lessee and inasmuch that the Lessee
         may have failed to effect such payment on due date thereof, the Lessee
         shall also be liable to pay the Lessor arrears interest on the amount
         so in arrears at the Libor rate applicable at such time plus 3% per
         month to date of actual payment. The receipt of the interest by the
         Lessor shall be in addition to its rights under this Agreement and
         under any law and the receipt thereof shall not be and shall not be
         considered as any waiver of any rights accorded to it in pursuance of
         this Agreement or under any law.

10.      Upon the expiration of the Lease or Option Period or termination
         thereof as defined in paragraph 2 above, as the case may be, the Lessee
         undertakes to restore the Premises and the appurtenances therein to the
         same condition as they had been received after effecting the
         alterations to the Basic Condition of the Premises and prior to
         carrying out any Further Alterations (if any), including re-painting
         and cleaning as set forth in paragraph 3 above, save for normal wear
         and tear resulting from ordinary and reasonable use or deterioration
         caused to the Premises during

<PAGE>

         the Lease Period, notwithstanding ordinary and reasonable use by the
         Lessee or by a person on its behalf or under its authority, or as a
         result of VIS MAJOR.

11.      The Lessee shall be liable for damage caused as a result of the lease
         and the use of the Premises by it and/or by its agents and/or by its
         invitees and/or any person on its behalf. The Lessee shall repair any
         damage as aforesaid in accordance with the Lessor's requirements.

12.      The Lessee is an insured within the framework of the insurance held by
         the RAD-Bynet Group and shall remain such an insured for the entire
         Lease Period as shall be customarily applied by the Group from time to
         time.

13.      The Lessee shall be entitled to transfer any part of its rights in and
         to the Premises only to a sub-lessee within the RAD-Bynet Group
         (hereinafter : "the Sub-Lessee"). In any event the Lessee shall
         continue to be responsible for all its obligations under this Agreement
         with respect to the whole area of the Premises as a guarantor for the
         fulfilment by the Sub-Lessee of all the provisions of this Agreement.

14.      Should the level of the holdings of Yehuda Zisapel and Zohar Zisapel
         decline, directly or indirectly below 25% of the issued share capital
         of the Lessee, and this as a guarantee for the fulfilment of all the
         obligations of the Lessee under this Agreement, the Lessee shall
         deposit with the Lessor, immediately upon receipt of the Lessor's
         initial request, and to its order, an autonomous unconditional,
         transferable bank guarantee, capable of foreclosure in its entirely or
         in instalments at any time without furnishing reasons therefor; in an
         amount in new Israeli shekels equal to 3 months rental, calculated at
         the rate applicable at the time of the issue of such bank guarantee.
         The guarantee shall be linked to the Consumer Price Index. The
         guarantee shall be valid for the entire Lease Period then remaining at
         the time of receipt of the Lessor's initial request, plus 3 months, and
         the validity thereof shall be renewed from time to time, one month
         prior to the date on which such validity is due to lapse, until the
         expiration of the Option Period plus 3 months after the expiration of
         such Option Period. The guarantee shall be duly stamped and all costs
         involved in the issue thereof shall be due solely be the Lessee.

15. Remarks :

         ---------------------------------------------------------
         ---------------------------------------------------------
         ---------------------------------------------------------

<PAGE>

RADVISION LTD.       ZISAPEL PROPERTIES           KLIL & MICHAEL PROPERTIES
                     (1992) LTD.                 (1992) LTD.

------------------   ----------------------       -----------------------------
The Lessee           Zisapel Properties           Klil & Michael Properties
                     (1992) Ltd.                  (1992) Ltd.

<PAGE>

                                    ANNEX A

[This exhibit consists of a two dimensional floor plan for the leased premises
(an area of 880 square meters on Level B) at 24 Raoul Wallenberg Street
Tel Aviv Israel. The floor plan shows a cross sectional view of room divisions
within the premises.]

<PAGE>

                                     ANNEX B

Schedule of the Works Required         AN ESTIMATE OF THE COST (IT IS NECESSARY
to be Undertaken                       TO ATTACH PLANS AS REQUIRED BY THE
                                       LESSOR) OF THE WORKS IN NEW ISRAELI
                                       SHEKELS / DOLLARS

Total amount of the Works ___________ new Israeli shekels / dollars

I approve the Works and the cost thereof, as set forth in this Annex.

-----------------------------       -------------------------      ----------
Zisapel Properties (1992) Ltd.      Klil & Michael Properties      The Lessee
                                    (1992) Ltd.

<PAGE>

                                 ANNEX C

Summary of agreement with the management company--translated from Hebrew
original

Management Company: Ariel Properties--ZIV Towers Management Ltd.

Building:    24 Raoul Wallenberg Street Tel Aviv Israel.

Services:    Providing maintenance services to the shared area in the building.

Fees:    Each tenant will pay the pro rata cost of its share in the shared
areas, according to actual costs paid by the management company plus 10%,
(provided such costs are reasonable and as customary in similar buildings).
Such fees will be paid quarterly.

<PAGE>

                                    AMENDMENT

To the Lease Agreement between the companies Zisapel Properties (1992) Ltd. and
Klil & Michael Properties (1992) Ltd., and the company RADVision dated 15th
January 1998 (hereinafter : "the Agreement"), made and entered into on 31st
December 1997.

The parties agree that with effect from 1st September 1998, an area of 206
square metres shall be added to the Premises (hereinafter : "the First
Additional Area of the Premises") marked in yellow on the diagram attached
hereto, and with effect from   a further area of   square metres shall be
added to the Premises (hereinafter : "the Second Additional Area") marked in
green on the diagram attached to this Amendment, with effect from 1st September
1998 the area of the Premises set forth in paragraph 1 of the Agreement shall be
changed and shall be 1086 square metres and not as it appears in the Agreement.

There are no other changes to the provisions of the Agreement.

For the sake of clarity the amount of the rental under paragraph 5.1 of the
Agreement shall be calculated as if the further area of the Premises had been
leased with effect from signature of the Agreement.

______________    ______________________________     _________________________
  The Lessee      Zisapel Properties (1992) Ltd.     Klil & Michael Properties
RADVision Ltd.                                       (1992) Ltd.

<PAGE>

                                     DIAGRAM

  [Diagram of an area of 206 square meters (the First Additional Area) marked
  in yellow and further area marked in green (the Second Additional Area),
  totaling 1,086 square meters]

<PAGE>

                                    AMENDMENT

To the Lease Agreement between the companies Zisapel Properties (1992) Ltd. and
Klil & Michael Properties (1992) Ltd., and the company RADVision dated 15th
January 1998 (hereinafter : "the Agreement"), made and entered into on 31st
December 1997.

The parties agree that with effect from 2nd May 1999, an area of 412 square
metres shall be added to the Premises (hereinafter : "the First Additional Area
of the Premises") marked in yellow on the diagram attached hereto and with
effect from a further area of   square metres shall be added to the
Premises (hereinafter : "the Second Additional Area") marked in green on the
diagram attached to this Amendment, with effect from 2nd May 1999 the area of
the Premises set forth in paragraph 1 of the Agreement shall be changed and
shall be 1498 square metres and not as it appears in the Agreement. Furthermore,
with effect from 2nd May 1999, 10 covered parking bays shall be added.
Accordingly the number of parking bays leased shall be 33, of which 33 shall be
charged at $ 90 and of which   shall be charged at $     .

There are no other changes to the provisions of the Agreement.

For the sake of clarity the amount of the rental under paragraph 5.1 of the
Agreement shall be calculated as if the further area of the Premises had been
leased with effect from signature of the Agreement.

RADVISION LTD.       ZISAPEL PROPERTIES           KLIL & MICHAEL PROPERTIES
                     (1992) LTD.                 (1992) LTD.

------------------   ----------------------       -----------------------------
The Lessee           Zisapel Properties           Klil & Michael Properties
                     (1992) Ltd.                  (1992) Ltd.

<PAGE>

                                     DIAGRAM

  [Diagram of an area of 412 square meters (the First Additional Area) marked
  in yellow and further area (the Second Additional Area) marked in green,
  totaling 1,498 square meters]

<PAGE>

                          AMENDMENT TO LEASE AGREEMENT

             Made and entered into at Tel Aviv on 1st December 1999

On 31st December 1997 a lease agreement was entered into between Zisapel
Properties (1992) and the company Klil & Michael Properties (1992) Ltd., and the
company RADVision Ltd for the lease of an area of 880 square metres, for the
lease of a further area of 206 square metres with effect from 1st September
1998, and for the lease of a further area of 412 square metres with effect from
2nd May 1999, and in the aggregate for the lease of an inclusive area of 1498
square metres, and for the lease of 33 parking bays ("the Lease Agreement").

The parties hereby agree to extend the Lease Agreement until 31st August 2000.

Paragraph 5.1 of the Lease Agreement shall be changed as follows :

An amount in new Israeli shekels equal to US $ 16.50 per square metre. An amount
in new Israeli shekels equal to US $ 110 per parking bay. The rest of the
provisions of this paragraph shall remain unchanged.

No change in the rest of the provisions of the Agreement.

----------------------     -----------------------------     ------------------
Zisapel Properties         Klil & Michael Properties         RADVision Ltd.
(1992) Ltd.                (1992) Ltd.

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