An attempt was made to compare the toxic effects of the organochlorine insecticide 'chlordane' in man and rats. Analysis of blood for chlordane metabolites showed their presence in the descending order of trans-nonachlor, oxychlordane, heptachlorepoxide and cis-nonachlor. The total range of chlordane and its metabolites in the sera of workers was 9.84 +/- 4.47 ng/g. Serum levels of triglycerides (TG), creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) activities were also found to be higher in pest-control operators. In a simultaneous study, rats were administered 100 mg/kg body wt. of chlordane by stomach tube once a day for 4 days, whereas 50 mg/kg body wt. of chlordane was injected intraperitoneally once a day for 4 days. The data show that total cholesterol and serum TG as well as CPK and LDH activities are increased after chlordane treatment. The isoenzyme patterns suggest that an increase in CPK and LDH is related to skeletal muscle. Furthermore, the hepatotoxicity of chlordane was also studied in rats only. A significant increase in liver weight, its water content, total lipids, triglycerides and phospholipids was recorded. Chlordane induced lipid peroxidation in the liver, exhibiting a dose-response relationship. Although no appreciable effect on mitochondrial function and latent ATPase activity was observed, 2,4-dinitrophenol-stimulated ATPase activity was inhibited. Histological examination of the liver confirmed fatty infiltration induced by chlordane in rats.