The main objective of this study was to conduct a risk assessment based on exposure data collected from pharmaceutical research scientists and veterinarians in San Diego, CA who are occupationally exposed to isoflurane gas. To achieve the objective, it was necessary to determine the dose-response relationship from literature values on the toxicology of isoflurane, and then through an exposure assessment, perform a risk assessment. Currently, occupational exposure to anesthetic gases occurs in the health sector, such as hospital operating rooms, veterinary clinics, and pharmaceutical research laboratories. According to California OSHA 5155 Table AC-1 Permissible Exposure Limits for Chemical Contaminants, the employer shall assure that no employee is exposed to an 8-hour timeweighted average (TWA) concentration of airborne isoflurane in excess of 2 parts per million parts of air. Between January 2006 and January 2013 isoflurane exposure data was collected from pharmaceutical research and veterinary facilities located in San Diego, CA. Isoflurane samples were analyzed by modified OSHA Method 07. The results show that the mean time weighted average concentration of isoflurane gas exposure in a pharmaceutical research laboratory was 0.62 ppm. The maximum recorded exposure concentration from the data pool was 1.64 ppm. The mean time weighted average concentration of isoflurane gas exposure for the veterinary clinics was 2.14 ppm. The maximum recorded exposure concentration from the veterinary data pool was 2.77 ppm. The hazard index (HI) is defined as the ratio of the exposure concentration over the reference dose. The hazard index, calculated from the average daily dose (mean TWA of 1.33 mg/kg-day), of the pharmaceutical research population was 0.06. The hazard index for this population's maximum recorded exposure concentration was 0.16. The hazard index of the veterinary population (average daily dose mean TWA of 0.21 mg/kg-day) was 0.21. The hazard index for this population's maximum recorded exposure concentration was 0.28. If the HI is less than 1, then the health effects are assumed not to be of concern, however, if the hazard quotient is greater than 1, then health effects may be assumed to occur. Based on the data collected in this study, the hazard indices for both the pharmaceutical research laboratories and veterinary clinics mean, as well as, maximum concentrations were all below a HI of 1.0, which confirms occupational exposure levels in these populations would not be expected to cause harmful health effects.