This study assessed possible adverse immunological effects of trans-1,2-dichloroethylene (DCE) on random-bred CD-1 mice following 14 and 90 days of exposure. A 14-day range-finding study was performed on male mice by gavage at doses 1/10 and 1/100 the LD50 (210 and 21 mg/kg). No alterations in either humoral or cell-mediated immunity were observed following this exposure. A 90-day study was conducted in which DCE was administered in the drinking water of male and female mice. The levels of DCE in the drinking water were calculated to deliver levels equivalent to, and higher than, those delivered for 14 days (17, 175, and 387 mg/kg for males and 23, 224, and 452 mg/kg for females). No changes were observed in the cell-mediated immune status of either sex or in the humoral immune status of females. However, a marked suppression in humoral immune status was observed in male mice exposed to all three levels of DCE, as indicated by a decreased ability of spleen cells to produce antibody against sheep erythrocytes (sRBC). Macrophage function was depressed only in females, as indicated by the decreased ability of thioglycollate-recruited peritoneal exudate cells (PEC) to phagocytize sRBC.