Formed in 1995 by EPA, several other federal and state agencies, and several private organizations, the National Advisory Committee on Acute Exposure Guideline Levels for Hazardous Substances (referred to as the NAC) develops, reviews, and approves acute exposure guideline levels (AEGLs) for up to 400 extremely hazardous substances (EHSs). AEGLs have a broad array of potential applications for federal, state, and local governments and for the private sector. They are necessary for prevention and emergency-response planning for potential releases of EHSs, either from accidents or as a result of terrorist activities. This report includes an assessment of the NAC’s draft AEGLs documents for the following 10 chemicals: 1, 4-dioxane; chloroform; carbon tetrachloride; sulfur dioxide; cis, trans 1,-2 dichloroethylene; monochloroacetic acid; carbon monoxide; fluorine; methanol; and phenol.