Exhibit 10.18

AMENDMENT NO. 1
TO LEASE

        THIS AMENDMENT NO. 1 is made and entered into this 18th day of July,
2001, by and between JOHN ARRILLAGA, Trustee, or his Successor Trustee UTA dated
7/20/77 (JOHN ARRILLAGA SURVIVOR'S TRUST) (previously known as the "Arrillaga
Family Trust") as amended, and RICHARD T. PEERY, Trustee, or his Successor
Trustee UTA dated 7/20/77 (RICHARD T. PEERY SEPARATE PROPERTY TRUST) as amended,
collectively as LANDLORD, and SYNOPSYS, INC., a Delaware corporation, as TENANT.

RECITALS

        A.    WHEREAS, by Lease Agreement dated August 24, 1995 Landlord leased
to Tenant all of that certain 85,000+/- square foot building located at
1101 West Maude Avenue, Mountain View, California, the details of which are more
particularly set forth in said August 24, 1995 Lease Agreement, and

        B.    WHEREAS, it is now the desire of the parties hereto to amend the
Lease by: (i) extending the Term for twelve years, thereby changing the
Termination Date from February 28, 2003 to February 28, 2015, (ii) amending the
Basic Rent schedule and Aggregate Rent accordingly, (iii) increasing the
Security Deposit required under the Lease, (iv) amending the Management Fee
charged to Tenant, (vii) replacing Lease Paragraphs 12 ("Property Insurance")
and 31 ("Notices"), (viii) amending Lease Paragraphs 5 ("Acceptance and
Surrender of Premises"), 6 ("Alterations and Additions"), 11 ("Tenant's Personal
Property Insurance and Workman's Compensation Insurance") and 21
("Destruction"), (xi) adding a paragraph ("Authority to Execute"), and (x)
deleting Lease Paragraphs 53 ("Two (2)—Three (3) Year Options to Extend") and 54
("Tenant's Option to Terminate Lease") to the Lease Agreement as hereinafter set
forth.

AGREEMENT

        NOW THEREFORE, for valuable consideration, receipt of which is hereby
acknowledged, and in consideration of the hereinafter mutual promises, the
parties hereto do agree as follows:

        1.     TERM OF LEASE: It is agreed between the parties that the Term of
said Lease Agreement shall be extended for an additional twelve (12) year period
(the "Extended Term"), and the Lease Termination Date shall be changed from
February 28, 2003 to February 28, 2015. The Extended Term of the Lease is
comprised of the two three year extensions (which extend the Term to
February 28, 2009) covered under Tenant's Option to Extend pursuant to Lease
Paragraph 53 ("Two Three Year Options to Extend") and an additional six year
extension, which extends the Term to February 28, 2015 to make the Termination
Date of this Lease co-terminous with the extended term of the Existing Leases as
referenced in Lease Paragraph 47 ("Lease Terms Co-Terminous"). Tenant and
Landlord hereby acknowledge Tenant's exercise of said Options to Extend the
Terms of said Lease, and Lease Paragraph 53 is hereby deleted in its entirety
upon the execution of this Amendment No. 1.

        2.     BASIC RENTAL FOR EXTENDED TERM OF LEASE: The monthly Basic Rental
for the Extended Term of Lease shall be as follows:

        On March 1, 2003, the sum of ONE HUNDRED FORTY THOUSAND TWO HUNDRED
FIFTY AND NO/100 DOLLARS ($140,250.00) shall be due, and a like sum due on the
first day of each month thereafter through and including February 1, 2004.

        On March 1, 2004, the sum of ONE HUNDRED FORTY FOUR THOUSAND FIVE
HUNDRED AND NO/100 DOLLARS ($144,500.00) shall be due, and a like sum due on the
first day of each month thereafter through and including February 1, 2005.

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        On March 1, 2005, the sum of ONE HUNDRED FORTY EIGHT THOUSAND SEVEN
HUNDRED FIFTY AND NO/100 DOLLARS ($148,750.00) shall be due, and a like sum due
on the first day of each month thereafter through and including February 1,
2006.

        On March 1, 2006, the sum of ONE HUNDRED FIFTY THREE THOUSAND AND NO/100
DOLLARS ($153,000.00) shall be due, and a like sum due on the first day of each
month thereafter through and including February 1, 2007.

        On March 1, 2007, the sum of ONE HUNDRED FIFTY SEVEN THOUSAND TWO
HUNDRED FIFTY AND NO/100 DOLLARS ($157,250.00) shall be due, and a like sum due
on the first day of each month thereafter through and including February 1,
2008.

        On March 1, 2008, the sum of ONE HUNDRED SIXTY ONE THOUSAND FIVE HUNDRED
AND NO/100 DOLLARS ($161,500.00) shall be due, and a like sum due on the first
day of each month thereafter, through and including February 1, 2009.

        On March 1, 2009, the sum of TWO HUNDRED SIXTEEN THOUSAND EIGHT HUNDRED
SIXTY TWO AND 67/100 DOLLARS ($216,862.67) shall be due, and a like sum due on
the first day of each month thereafter, through and including February 1, 2010.

        On March 1, 2010, the sum of TWO HUNDRED TWENTY TWO THOUSAND TWO HUNDRED
EIGHTY FOUR AND 24/100 ($222,284.24) shall be due, and a like sum due on the
first day of each month thereafter, through and including February l, 2011.

        On March 1, 2011, the sum of TWO HUNDRED TWENTY SEVEN THOUSAND EIGHT
HUNDRED FORTY ONE AND 34/100 DOLLARS ($227,841.34) shall be due, and a like sum
due on the first day of each month thereafter, through and including February 1,
2012.

        On March 1, 2012, the sum of TWO HUNDRED THIRTY THREE THOUSAND FIVE
HUNDRED THIRTY SEVEN AND 38/100 DOLLARS ($233,537.38) shall be due, and a like
sum due on the first day of each month thereafter, through and including
February 1, 2013.

        On March 1, 2013, the sum of TWO HUNDRED THIRTY NINE THOUSAND THREE
HUNDRED SEVENTY FIVE AND 81/100 DOLLARS ($239,375.81) shall be due, and a like
sum due on the first day of each month thereafter, through and including
February 1, 2014.

        On March 1, 2014, the sum of TWO HUNDRED FORTY FIVE THOUSAND THREE
HUNDRED SIXTY AND 21/100 DOLLARS ($245,360.21) shall be due, and a like sum due
on the first day of each month thereafter, through and including February 1,
2015.

        The Aggregate Basic Rent for the Lease Term, as extended, shall be
increased by $27,486,139.80 or from $10,633,500.00 to $38,119,639.80.

        3.     SECURITY DEPOSIT: Provided Tenant is not in default (pursuant to
Paragraph 19 of the Lease, i.e. Tenant has received notice and any applicable
cure period has expired without cure) of any of the terms, covenants, and
conditions of the Lease Agreement, the Security Deposit required under the Lease
shall remain $280,500.00. In the event of a Tenant default, Tenant's Security
Deposit shall be increased by $210,220.42, or from $280,500.00 to $490,720.42 as
follows:

        A.    By February 28, 2003 (or within ten (10) days of notice from
Landlord of an uncured default under the Lease if said default occurs after
February 28, 2003), Tenant shall: (i) provide Landlord with an amended Standby
Letter of Credit, in compliance with the terms of Lease Paragraph 44 ("Security
Deposit Represented by Standby Letter of Credit") in the total amount of
$297,500.00, which amount is the Security Deposit required under Tenant's First
Three Year Option to Extend as stated in Lease Paragraph 53.A; or (ii) deposit
cash in the amount of $17,000.00.

        B.    By February 28, 2006 (or within ten (10) days of notice from
Landlord of an uncured default under the Lease if said default occurs after
February 28, 2006), Tenant shall: (i) provide Landlord with an amended Standby
Letter of Credit, in compliance with the terms of Lease

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Paragraph 44 ("Security Deposit Represented by Standby Letter of Credit") in the
total amount of $323,000.00, which amount is the Security Deposit required under
Tenant's Second Three Year Option to Extend as stated in Lease Paragraph 53.B;
or (ii) deposit cash in the amount of $25,500.00.

        C.    By February 28, 2009 (or within ten (10) days of notice from
Landlord of an uncured default under the Lease if said default occurs after
February 28, 2006), Tenant shall: (i) provide Landlord with an amended Standby
Letter of Credit, in compliance with the terms of Lease Paragraph 44 ("Security
Deposit Represented by Standby Letter of Credit") in the total amount of
$490,720.42, which amount is the total Security Deposit required under the
Lease; or (ii) deposit cash in the amount of $167,720.42.

        Within ten (10) business days of Tenant's execution of this Amendment
No. 1, Tenant shall provide Landlord with an amended Standby Letter of Credit
reflecting an expiration date on the Standby Letter of Credit of March 30, 2015.

        4.     MANAGEMENT FEE: Effective March 1, 2009, and on the first day of
each month thereafter during said Lease Term, Tenant shall pay to Landlord, in
addition to the Basic Rent and Additional Rent, a fixed monthly management fee
("Management Fee") equal to one and one-half percent (1.5%) of the Basic Rent
due for each month throughout the remaining Lease Term. Notwithstanding anything
to the contrary above or in Lease Paragraph 4.D ("Additional Rent"), no
additional real property management fee shall be charged to Tenant.

        5.     PROPERTY INSURANCE: Lease Paragraph 12 ("Property Insurance") is
hereby deleted in its entirety and shall be replaced with the following:

        "12: PROPERTY INSURANCE. Landlord shall purchase and keep in force, and
as Additional Rent and in accordance with Paragraph 4D of this Lease, Tenant
shall pay to Landlord (or Landlord's agent if so directed by Landlord) Tenant's
proportionate share (allocated to the Leased Premises by square footage or other
equitable basis as calculated and determined by Landlord) of the deductibles on
insurance claims and the cost of, policy or policies of insurance covering loss
or damage to the Premises (including all improvements within the Premises
constructed by either Landlord or Tenant (provided Tenant has obtained
Landlord's written approval for said improvements to the Premises) and Complex
(excluding routine maintenance and repairs and incidental damage or destruction
caused by accidents or vandalism for which Tenant is responsible under
Paragraph 7) in the amount of the full replacement value thereof, providing
protection against those perils included within the classification of "all
risks" insurance and flood and/or earthquake insurance, if available, plus a
policy of rental income insurance in the amount of one hundred (100%) percent of
twelve (12) months Basic Rent, plus sums paid as Additional Rent and any
deductibles related thereto. If such insurance cost is increased due to Tenant's
use of the Premises or the Complex, Tenant agrees to pay to Landlord the full
cost of such increase. Tenant shall have neither interest in nor any right to
the proceeds of any insurance procured by Landlord for the Complex.

        In addition and notwithstanding anything to the contrary in this
Paragraph 12, each party to this Lease hereby waives all rights of recovery
against the other party or its officer, employees, agents and representatives
for loss or damage to its property or the property of others under its control,
arising from any cause insured against under the fire and extended coverage
(excluding, however, any loss resulting from Hazardous Material contamination of
the Property) required to be maintained by the terms of this Lease Agreement to
the extent full reimbursement of the loss/claim is received by the insured
party. Each party required to carry property insurance hereunder shall cause the
policy evidencing such insurance to include a provision permitting such release
of liability ("waiver of subrogation endorsement") provided, however, that if
the insurance policy of either releasing party prohibits such waiver, then this
waiver shall not take effect until consent to such waiver is obtained; provided,
however, that if the insurance policy of either releasing party prohibits such
waiver, then this waiver shall not take effect until consent to such waiver is
obtained. If such waiver is so prohibited, the insured party affected shall
promptly notify the other party thereof. In the' event the waivers are issued to
the parties and are not valid under current policies and/or subsequent insurance
policies, the

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non-complying party will provide, to the other party, 30 days advance
notification of the cancellation of the subrogation waiver, in which case
neither party will provide such subrogation waiver thereafter and this Paragraph
will be null and void. The foregoing waiver of subrogation shall not include any
loss resulting from Hazardous Material contamination of the Property or any
insurance coverage relating thereto."

        6.     NOTICES: Lease Paragraph 31 ("Notices") is hereby deleted in its
entirety and shall be replaced with the following:

        "31. NOTICES. All notices, demands, requests, advices or designations
which maybe or are required to be given by either party to the other hereunder
shall be in writing. All notices, demands, requests, advices or designations by
Landlord to Tenant shall be sufficiently given, made or delivered if personally
served on Tenant by leaving the same at the Premises (provided written receipt
is offered and is addressed to the attention of the Vice President of Real
Estate) or if sent by United States certified or registered mail, postage
prepaid or by a reputable same day or overnight courier service addressed to
Tenant at: SYNOPSYS, INC., 700 EAST MIDDLEFIELD ROAD, MOUNTAIN VIEW, CA 94043,
ATTN: VICE PRESIDENT OF REAL ESTATE. As an accommodation to Tenant, Landlord
shall also send a copy of all notices to: SHARTSIS, FRIESE & GINSBURG LLP, ONE
MARITIME PLAZA, 18TH FLOOR, SAN FRANCISCO, CA 94111, ATTN: JONATHON M. KENNEDY;
however, Tenant acknowledges and agrees that any notice delivered to Tenant's
main address listed above shall be considered to be delivered to Tenant,
regardless of whether or not said notice is submitted and/or received at the
secondary address. All notices, demands, requests, advices or designations by
Tenant to Landlord shall be sent by United States certified or registered mail,
postage prepaid, addressed to Landlord at its offices at: PEERY/ARRILLAGA, 2560
MISSION COLLEGE BLVD., SUITE 101, SANTA CLARA, CA 95054. Each notice, request,
demand, advice or designation referred to in this Paragraph shall be deemed
received on the date of the personal service or receipt or refusal to accept
receipt of the mailing thereof in the manner herein provided, as the case may
be. Either party shall have the right, upon ten (10) days written notice to the
other, to change the address as noted herein."

        7.     ALTERATIONS MADE BY TENANT: The provisions of this Paragraph 7
shall modify Lease Paragraphs 5 ("Acceptance and Surrender of Premises") and 6
("Alterations and Additions"), as follows:

        A.    Landlord acknowledges that Tenant shall have the right, subject to
the terms of this Paragraph 7.A, to make non-structural, interior improvements
("Interior Improvements") to the Premises subject to the following:

        a)    Tenant shall provide Landlord, for Landlord's approval, a set of
construction plans and a list reflecting the Interior Improvements Tenant
desires to make to the Increased Premises no later than November 1, 2002. Upon
Landlord's review and approval of said Interior Improvements, said construction
plans shall become Exhibit B-1 to this Lease. Construction of said Interior
Improvements shall not commence until Landlord and Tenant execute Landlord's
standard Consent to Alterations agreement and Landlord has posted its Notice of
Non-Responsibility;

        b)    Landlord shall not be required, under any circumstance, to
contribute any concessions or monetary contribution to said Interior
Improvements;

        c)     Tenant shall not be required to remove the Landlord approved
Interior Improvements shown on Exhibit B-1 at the expiration or earlier
termination of the Lease Term. Notwithstanding anything to the contrary herein,
Landlord's approval of said Interior Improvements referenced in Section 7.A
(a) above may provide for specific Interior Improvements to be restored of the
expiration or earlier termination of the Lease Term if said Interior
Improvements are not consistent with Landlord's standard interior improvements.

        B.    Notwithstanding anything to the contrary in Lease Paragraph 6
("Alterations and Additions"), Landlord's written consent to any future
alterations or additions to the Premises will

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specify whether Landlord shall require removal of said alterations and/or
additions, provided Tenant requests such determination from Landlord:

        8.     TENANT'S PERSONAL PROPERTY INSURANCE AND WORKMAN'S COMPENSATION
INSURANCE. The provisions of this Paragraph 8 shall modify Lease Paragraph 11
("Tenant's Personal Property Insurance and Workman's Compensation Insurance"),
as follows: Tenant's obligation to insure the leasehold improvements owned by
Tenant within the Leased Premises shall be limited to those leasehold
improvements owned by Tenant that are not covered by real property insurance
Landlord obtains pursuant to Lease Paragraph 12 ("Property Insurance") as
amended in Paragraph 5 above.

        9.     DESTRUCTION. The provisions of this Paragraph 9 shall modify
Lease Paragraph 21 ("Destruction"), as follows: Landlord's obligation to rebuild
or restore the Premises shall be limited to the building and any interior
improvements covered by the real property insurance Landlord obtains pursuant to
Lease Paragraph 12 ("Property Insurance") as amended in Paragraph 5 above.

        10.   AUTHORITY TO EXECUTE. The parties executing this Agreement hereby
warrant and represent that they are properly authorized to execute this
Agreement and bind the parties on behalf of whom they execute this Agreement and
to all of the terms, covenants and conditions of this Agreement as they relate
to the respective parties hereto.

        11.   TENANT'S OPTION TO TERMINATE LEASE: Lease Paragraph 54 ("Tenant's
Option to Terminate Lease") is hereby deleted in its entirety, and shall be of
no further force or effect.

        EXCEPT AS MODIFIED HEREIN, all other terms, covenants, and conditions of
said August 24, 1995 Lease Agreement shall remain in full force and effect.

        IN WITNESS WHEREOF, Landlord and Tenant have executed this Amendment
No. 1 to Lease as of the day and year last written below.

LANDLORD:

JOHN ARRILLAGA SURVIVOR'S TRUST   TENANT:

SYNOPSYS, INC.
a Delaware corporation
By
/s/ JOHN ARRILLAGA

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John Arrillaga, Trustee
 
By
/s/ AART DE GEUS

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AART DE GEUS Date: 8/8/01    

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Print or Type Name       Title: CHAIRMAN & CEO       Date: 8/8/01
RICHARD T. PEERY
SEPARATE PROPERTY TRUST
 
 
 
By
/s/ JASON PEERY

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Jason Peery, Special Trustee
 
 
  Date: 8/8/01      

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