JOINT FILING AGREEMENT

Exhibit 99.1

JOINT FILING AGREEMENT

          In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, each of the undersigned hereby agrees that a statement on Schedule 13D relating to the Common Stock, par value US$0.01 per share, of Aspect Medical Systems, Inc. is being filed with the Securities and Exchange Commission on behalf of each of them.

Dated: March 12, 2009     

FIRST MANHATTAN CO.
By FIRST MANHATTAN LLC,
   General Partner

By:     /s/ Xxxx X. Xxxxxxx     
Name:   Xxxx X. Xxxxxxx
Title:     Managing Member

FIRST BIOMED MANAGEMENT ASSOCIATES, LLC
By FIRST MANHATTAN CO.,
   Co-Managing Member
By FIRST MANHATTAN LLC,
   General Partner

By:     /s/ Xxxx X. Xxxxxxx     
Name:   Xxxx X. Xxxxxxx
Title:     Managing Member

          /s/ Xxxxxxx X. Xxxxxxx     
                Xxxxxxx X. Xxxxxxx