The purpose of this study was to assess the immunological effects of 1,1,2-trichloroethane (TCE) on random-bred CD-1 mice following 14 and 90 days of oral exposure. A toxicological evaluation conducted at the same time revealed the target organs to be the liver of both sexes and the erythroid elements of the females. The 14-day immunological range-finding study in males exposed to doses 1/10 and 1/100 the LD50 (38 and 3.8 mg/kg) revealed no alterations in either humoral or cell-mediated immune status. Following 90 days of exposure in the drinking water (4.4., 46, and 305 mg/kg for males and 3.9, 44, and 384 mg/kg for females), a more detailed series of immunological parameters was assessed. Cell-mediated immunity was unaltered in both sexes, while humoral immune status was depressed in both sexes, particularly when determined by hemagglutination titers. Macrophage function was depressed only in the males as indicated by the ability of thioglycolate-recruited peritoneal exudate cells (PEC) to phagocytize sheep erythrocytes (sRBC).