Chlorfenvinphos, 2-chloro-1-(2,4-dichlorofenyl)vinyl diethyl phosphate, is an organophos-phate insecticide widely used in Poland singly or in mixture. The present study was undertaken to determine chlorfenvinphos-induced lipid peroxidation and to show whether acute intoxication with chlorfenvinphos alters the antioxidant system in the erythrocytes and serum. The study was conducted on male Wistar rats divided into two groups. The animals of control group were given olive oil intragastrically by a stomach tube, the animals of experimental group received oil solution of chlorfenvinphos (CVP) at a dose of 0.02, 0.1 or 0.5LD50. The blood was collected via heart puncture at the 1st, 24th and 48th hour after treatment. We determined the erythrocytes concentration of glutathione, the activities of glutathione peroxidase, glutathione reductase and glucose-6-phosphate dehydrogenase as well as the serum concentration of ascorbic acid, á-to-copherol and malondialdehyde. We observed the stimulation of enzymatic and nonenzymatic antioxi-dant system and lipid peroxidation in the erythrocytes and serum of chlorfenvinphos intoxicated rats.