Trans-1,2-dichloroethylene (DCE) was administered to male and female CD-1 mice in order to evaluate its effects on standard toxicological parameters. Following an acute LD50 determination (2122 mg/kg in males and 2391 mg/kg in females) and a 14-day range-finding study, a 90-day drinking water study was performed using levels of DCE calculated to deliver approximately 1/100, 1/10, and 1/5 the LD50. Various toxicological assessments were made, including body and organ weights, hematology, serum chemistries, and hepatic microsomal activities. Few alterations were observed in either sex following 90 days of exposure. The most noteworthy changes occurred in the males exposed to the highest level of DCE, where there was a significant decrease in glutathione levels, and in the females exposed to all three DCE levels, where there was a significant decrease in aniline hydroxylase activity. These data served as background for the immunotoxicological evaluation presented in the following manuscript.