In order to clarify the cytotoxicity of chlordane (industrial product as insecticide), the effect on oxidative phosphorylation in rat liver mitochondria was studied. The respiration rate. RCI and ADP/O ratio were inhibited by chlordane related compounds, and the degree of inhibition was in the descending order of trans-chlordane, cis-chlordane, heptachlor and heptachlor epoxide. Of the indexes indicating various respiratory activities, state 3 respiration was the most sensitively inhibited by these compounds, suggesting their energy transfer inhibition. However, electron transport was also inhibited by high concentrations of chlordane constituents. The inhibitory effect of the chlordane constituents on respiratory activity varied depending on the species of respiratory substrate, suggesting site specificity of these compounds. Trans-chlordane, cis-chlordane and heptachlor stimulated Mg(2+) ATPase activity and inhibited DNP-stimulated ATPase activity. Heptachlorepoxide, a metabolic product of heptachlor, has less effect on mitochondria than heptachlor.