Mature male Wistar rats (weighing 300-320 g and each group six animals) were given malathion (27 mg/kg; 1/50 of the LD50 for an oral dose), vitamin C (200 mg/kg)+vitamin E (200 mg/kg), or both daily via gavage for 4 weeks. At the end of the fourth week, the malathion-treated group and the malathion plus vitamin-treated group both had significantly higher white blood cell (WBC) and thrombocyte counts than the control group. Compared to the control group, the two groups also had significantly higher serum total cholesterol, alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) levels, and significantly lower triglyceride and very low density lipoprotein (VLDL) levels. The malathion-treated rats also had significantly lower serum total protein and albumin levels, but the malathion plus vitamin-treated group did not differ from the control group in terms of these parameters. Moreover, concomitant vitamin treatment significantly normalized, at least partially, all of the other hematological and biochemical parameters that were altered by malathion. Light microscopic analyses revealed that both the malathion-treated and malathion plus vitamin-treated groups exhibited histopathological changes in liver tissues, although some pathological features were only observed in the malathion-treated group. Thus, vitamins C and E can reduce malathion hepatotoxicity, although the degree of protection they provide is limited.