Commonly used organophosphate pesticide dichlorvos is known to cause neurologic lesions. However, the exact mechanism of its neurotoxicity is, as yet, unclear. Using dose-dependent inhibition of acetylcholinesterase activity as an index of its neurotoxicity, effects of three different doses of dichlorvos (0.6 mg, 1.5 mg, and 3.0 mg/kg body weight i.p. daily for 10 days) have been observed on the rate of lipid-peroxidation in the cerebrum, cerebellum and brain stem of albino rats. Simultaneously, electron microscopic study of the dichlorvos intoxicated rat cerebellum was also carried out. Dose-dependent increase in the rate of lipid peroxidation was found in all the brain regions, and increased incidence of lipofuscin-like pigment granules was discernible in the Purkinie cells of the cerebellar cortex.