The acute toxic effects of 1,1-dichloroethylene (DCE; 125 mg/kg, i.p.) on mouse lung, liver and kidney were investigated 24 hr after its administration. DCE caused a reduction of cytochrome P-450 levels and related monooxygenases in lung microsomes with no corresponding changes in liver and kidney. Examination of the lung tissue by light microscopy revealed necrosis restricted to the Clara cells. In contrast, liver and kidney were relatively unaffected by DCE treatment, as indicated by lack of changes in microsomal monooxygenase activities and morphology.