Suite 3400

Exhibit 99.1

Xxxxx 0000

000 Xxxxxxx Xxxxxx

Xxxxxxxxx, Xxxxxxx Xxxxxxxx

Xxxxxx, X0X 0X0

Telephone

(000) 000-0000

Facsimile

(000) 000-0000

xxx.xxxxxxxx.xxx

September 12, 2006

Xxxxxxx X. Jeannes
Executive Vice President, Administration
Glamis Gold Ltd.
0000 Xxxx Xxxx, Xxxxx 000
Xxxx, Xxxxxx
00000

Re: Goldcorp Inc. — Project Sahara

This letter agreement is to evidence that the undersigned have hereby agreed that the Arrangement Agreement among Goldcorp Inc., 0756808 B.C. Ltd. and Glamis Gold Ltd. dated August 30, 2006 (the “Arrangement Agreement”) in sections 4.02 (l) and Section 7.03 (h) to “September 13, 2006” is amended as and from September 12, 2006 by replacing the reference to “September 13, 2006” to “September 26, 2006”.

All other terms and conditions of the Arrangement Agreement remain in full force and effect, unamended.

Please sign this letter agreement where indicated and return an original to our attention to confirm your agreement with the amendments to the Arrangement Agreement set out herein.

Yours truly,

Goldcorp Inc. and 0756808 B.C. Ltd.
Per:
(Signed) Xxxxxxx Xxxx

Xxxxxxx Xxxx
Authorized Signing Representative

Acknowledged and agreed this 13^th day of September, 2006.

Glamis Gold Ltd.
Per:
(Signed) Xxxxx XxXxxxxx		(Signed) Xxxxxxx X. Jeannes
Xxxxx XxXxxxxx		Xxxxxxx X. Jeannes
President and Chief Executive Officer		Executive Vice President, Administration