The purpose of this publication is to facilitate the implementation of deployment occupational and environmental health surveillance requirements outlined in Department of Defense instruction (DODI) 6490.03 (Aug2006), Deployment Health, and the Joint Chiefs of Staff memorandum MCM 0028-07 (Nov2007), Procedures for Deployment Health Surveillance. In addition, this publication is intended to provide a standardized methodology for the military Services to support organic preventive medicine assets in successfully accomplishing an OEHSA in various deployed environments. This publication is designed for use at the tactical level. The document supports and applies to preventive medicine personnel across all military Services that are preparing for and conducting OEHSAs at military deployment locations. Occupational and Environmental Health Site Assessment provides guidance to deployed Service preventive medicine personnel who plan to conduct occupational and environmental health site assessments (OEHSAs) on military installations in a theater operational environment. This publication provides specific tactical references to facilitate the execution of an OEHSA to identify and document occupational and environmental health (OEH) threat conditions that may affect the current and future health of deployed military personnel.