Bentazone, a benzothiadiazole herbicide, is widely used for a variety of crops including cereals, maize, peas, rice and soy beans. The concern for human health is stil very high because bentazone is continuously monitored in environment and several studies to evaluate its potential carcinogenic effects when chronic and high doses were administered to animals. We aimed to investigate the possible effects of bentazone on lipid peroxidation, levels of glutathione and activities of antioxidant enzymes in human erythrocytes in vitro. For that, erythrocyte were incubated with bentazone in different concentrations (0-50 nM) at 37 degrees C for 1 hr. Bentazone showed significant increase in the levels of malondialdehyde (MDA) at the highest concentration in erythrocytes as an index of lipid peroxidation. Besides, alterations in the levels of reduced glutathione (GSH) and activities of glutathione peroxidase (GSH-Px) were observed while the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GSH-Rd) were unchanged. In conclusion, findings from this study indicate that in vitro toxicity of bentazone may be associated with oxidative stress and this work warrants further in vivo investigations.