Aspect Medical Systems’ Letter to the Editor Regarding Anesthesia Awareness Study Published in New England Journal of Medicine

Aspect Medical Systems (NASDAQ: ASPM), the global market leader in brain monitoring technology, today announced that the Company’s letter to the editor regarding a study and editorial evaluating use of BIS(R) technology to reduce the risk of anesthesia awareness was published in the July 24th issue of the New England Journal of Medicine (NEJM). The NEJM also published letters from Dr. Paul Myles and co-investigators from the Australian B-Aware trial published in The Lancet in 2004, Dr. Lulong Bo and colleagues from Changhai Hospital in China, Dr. Diamanto Aretha and colleagues from University Hospital of Patras in Greece, and Dr. Tim M. Cook, from Royal United Hospital in Bath, United Kingdom. Responses from Dr. Michael Avidan and colleagues, authors of the NEJM study, and Dr. Beverly A. Orser, author of the NEJM editorial, were also published. A link to view this correspondence is available at www.aspectmedical.com.

“The awareness study recently published in the New England Journal of Medicine has prompted significant discussion throughout the global anesthesia community concerning the role of brain monitoring and the issues associated with too little as well as too much anesthesia,” said Scott Kelley, M.D., anesthesiologist and vice president and medical director of Aspect Medical Systems. “We are pleased that many leading anesthesia researchers and thought leaders have expressed the need to consider a variety of outcomes, including avoiding awareness, in managing a patient’s anesthesia care.”

A recent editorial published in the British Journal of Anaesthesia (BJA) following the 7th International Symposium on Memory and Awareness, provided a current assessment of clinical strategies to avoid awareness, including the role of depth of anesthesia monitoring. Notably, in commenting upon the NEJM study, the BJA editorial emphasized that the end-tidal anesthetic gas protocol used in the NEJM study is not reflective of current standard practice, but in fact is an alternate practice change that might be considered by clinicians. A link to this editorial is available at www.aspectmedical.com.

“The BJA editorial also highlights the emerging concerns related to anesthesia exposure and states that the NEJM study results support the need to ‘modify contemporary practice’ with one of the approaches shown to reduce risk of awareness,” said Dr. Kelley. “Avoiding awareness is just one of many goals that anesthesia professionals seek and, given the extensive clinical evidence and our experience in monitoring more than 27 million patients worldwide, we believe that use of brain monitoring to help guide anesthetic titration while maintaining a BIS value of less than 60 is a very effective way to individualize care, minimize awareness and improve patient outcomes.”

More information related to the NEJM publication can be found at Aspect’s Web site at www.aspectmedical.com, including Aspect’s commentary on the Avidan study and a comparison of the awareness trials led by Dr. Paul Myles and Dr. Michael Avidan.

Aspect includes in this press release links to its Web site. Aspect cautions you that the information on this Web site is not incorporated by reference into this press release and should not be considered to be a part of this press release.

About Aspect Medical Systems, Inc.

Aspect Medical Systems, Inc. (NASDAQ: ASPM) is a global market leader in brain monitoring technology. To date, the Company’s Bispectral Index (BIS) technology has been used to assess approximately 27 million patients and has been the subject of approximately 3,000 published articles and abstracts. BIS technology is installed in approximately 79 percent of hospitals listed in the July 2008 U.S. News and World Report ranking of America’s Best Hospitals and in approximately 75 percent of all U.S. operating rooms. In the last twelve months BIS technology was used in approximately 19 percent of all U.S. surgical procedures requiring general anesthesia or deep sedation. BIS technology is available in more than 160 countries. Aspect Medical Systems has OEM agreements with nine leading manufacturers of patient monitoring systems. For more information, please visit the Aspect Medical Systems Web site www.aspectmedical.com.

Cautionary Statement Concerning Forward-Looking Information

Certain statements in this press release are forward-looking within the meaning of the Private Securities Litigation Reform Act of 1995 and may involve risks and uncertainties, including statements about the potential benefits of the Company’s brain monitoring technologies in helping anesthesia providers deliver anesthesia and in reducing the incidence of awareness and statements regarding the use and adoption of BIS monitoring technologies. There are a number of important factors that could cause actual results to differ materially from those indicated by these forward-looking statements. For example, future clinical trials and clinician use could demonstrate different and/or unfavorable results regarding the potential benefits of the Company’s brain monitoring product. The Company may also not be able to achieve widespread market acceptance of its BIS monitoring technology, or to compete with new products or alternative techniques that may be developed by others, including third-party anesthesia monitoring products approved by the FDA. Cases of awareness with recall during monitoring with the BIS system and significant product liability claims are among the factors that could limit market acceptance. The Company also faces competitive and regulatory risks relating to its ability to successfully develop and introduce enhancements and new products including the BIS VISTA monitor and products based upon its neuroscience technology. There are other factors that could cause the Company’s actual results to vary from its forward-looking statements, including without limitation those set forth under the heading “Risk Factors” in the Company’s Quarterly Report on Form 10-Q for the fiscal quarter ended March 29, 2008 as filed with the Securities and Exchange Commission.

In addition, the statements in this press release represent the Company’s expectations and beliefs as of the date of this press release. The Company anticipates that subsequent events and developments may cause these expectations and beliefs to change. However, while the Company may elect to update these forward-looking statements at some point in the future, it specifically disclaims any obligation to do so. These forward-looking statements should not be relied upon as representing the Company’s expectations or beliefs as of any date subsequent to the date of this press release. Aspect, Bispectral Index and BIS are registered trademarks of Aspect Medical Systems, Inc. All other trademarks, service marks and company names are the property of their respective owners.