Objective: To study the levels of malonyldialdehyde, marked as the concentration of substances reacting with thiobarbituric acid in liver, brain, serum and kidney in subacute intoxication with low doses of chlorfenvinphos,an organophosphate insecticide. Materials and Methods: The study used male Wistar rats, body weight 250 – 280g. The animals received intragastrically, by a gastric tube, once daily 0.1ml/100g of olive oil (the control group) or oil solution of chlorfenvinphos at a dose of 0.02LD₅₀ (0.3 mg/kg b.w.) (the experimental groups). After 14 and 28 days of the experiment,blood samples were collected by cardiac puncture to obtain serum; liver, kidney and brain sections were taken from the animals in anaesthesia. The level of malonyldialdehyde (as TBA RS) was determined in homogenates of the organs and in serum. Additionally, serum cholinesterase activity was determined. Results: There was an increase in the tissues as well in the serum malonyldialdehyde level. Proportionally the highest increase in TBARS , as compared to the control, was observed in the liver on day 28 of chlorfenvinphos administration and in the kidney on day 14 of the exposure. Conclusion: In subacute chlorfenvinphos intoxication, lipid peroxidation is increased in the rat liver, serum,kidney and brain, which may cause various health effects in the population exposed to its action.