The effects of organophosphate insecticide methidathion (MD) on kidney tissue and the ameliorating effects of a combination of vitamins E and C against subchronic MD toxicity were evaluated in rats. Experimental groups were: control group (group I), 5 mg/kg body weight MD-treated group (group II), and 5 mg/kg body weight MD plus vitamin E plus vitamin C treated group (group III). The groups II and III were treated orally with MD on five days a week for four weeks. Vitamins E and C were injected at doses of 50mg/kg body weight, i.m. and 20mg/kg body weight, i.p., respectively, 30 min after the treatment of MD in the group III. Rats were anaesthesized and venous blood samples were collected by direct right ventricle heart puncture, in addition, the right kidney was removed for histopathological examinations and malondialdehyde (MDA) analyses after four weeks. The serum activity of cholinesterase (ChE) and the kidney level of malondialdehyde, and kidney histopathology were studied in rats. MD caused decreased ChE activity (group I: 2114 +/- 63 U/L, group 11: 1455 +/- 100U/L) and increased MDA level (group II: 147 +/- 20.2nmol/mg protein, group 11: 236 +/- 25.6 nmol/mg protein), and kidney damage in rats. Furthermore, a combination of vitamins E and C restored partially (ChE activity: 1670 +/- 111 U/L, MDA level: 159 +/- 19.4 nmol/mg protein) this changes in MD-treated rats. (c) 2005 Elsevier Inc. All rights reserved.