LaSalle Bank LaSalle Bank N.A., ABN AMRO 135 S. LaSalle Street Chicago, IL 60603 Facsimile: 312/904-6457 george.kumis@abnamro .com George L. Kumis Senior Vice President Commercial Lending: Healthcare Industry

Exhibit 99.18

LaSalle Bank		LaSalle Bank N.A.,
ABN AMRO		000 X. XxXxxxx Xxxxxx
		Xxxxxxx, XX 00000
		312/904-8659
		Facsimile: 312/904-6457
		xxxxxx.kumis@abnamro .com
		Xxxxxx X. Xxxxx
		Senior Vice President
		Commercial Lending: Healthcare Industry

Acceptance of Request for Extension

December 22, 2006

Aetna Inc,
000 Xxxxxxxxxx Xxxxxx
Xxxxxxxx, XX 00000

Re: Amended and Restated Five-Year Credit Agreement dated as of January 20, 2006 (the “Credit Agreement”)

Attention: Xxxxxx X. Xxxxx, Vice President, Finance and Treasurer

Dear Al:

We have received your Extension Request, dated December 5, 2006, and pursuant to Section 2.06(c) (Maturity of Loans) of the above-referenced Credit Agreement, we hereby agree to the extension set forth in such request. Upon the effectiveness of the Extension Request in accordance with Section 2.06(c) of the Credit Agreement, the new Maturity Date will be January 20, 2012.

We have made a notation of this extension on the Schedule of Loans, Payments of Principal attached to our Syndicated Note(s).

Very truly yours,
LASALLE BANK NATIONAL ASSOCIATION
By:		/s/ Xxxxxx X. Xxxxx
		Name: Xxxxxx X. Xxxxx
		Title: Senior Vice President