The role of reactive oxygen species (ROS) in various diseases of the female reproductive tract has been shown, and oxidative stress is an important component of the mechanism of toxicity of Opts. Methyl parathion (MPT) is one of the most widely used organophosphate insecticides (Opts) in agriculture. The aim of the study was to elucidate the effect of subchronic NIPT exposure on lipid peroxidation and serum activities of cholinesterase (ChE), and the protective effects of combination of antioxidant Vitamins E and C in rats. Additionally, histopathological and immunohistochemical changes in endometrium were aimed to be examined. Three groups of rats were used in the experiment. The first group was treated with 5 mg/kg NIPT; the second group Was treated with 5 mg/kg body weight NIPT plus Vitamin E and Vitamin C (NIPT + Vit) and the third group was given only corn oil (control). NIPT and NIPT + Vit groups were given MPT by gavage 5 days a week for 4 weeks at a dose level of 4 mg/(kg day) by using corn oil as the vechicle. Vitamins E and C were injected at doses of 50 mg/kg i.m. and 20 mg/kg body weight i.p. Histopathological and immunohistochemical examinations for caspase-3 and caspase-9 were accomplished in the endometrium. The level of malondialdehyde (NIDA) increased significantly in the NIPT group compared with the control group (p < 0.05). NIDA significantly decreased in the NIPT + Vit group compared with the MPT group (p < 0.05). Administration of Vitamins E and C along with NIPT significantly reduced the histopathological changes and the extent of apoptosis. In conclusion, subchronic NIPT administration caused endometrial damage and that treatment with a combination of Vitamins E and C reduced endometrial damage caused by NIPT. (c) 2006 Elsevier B.V. All rights reserved.