Objectives: Selenium is an antioxidant nutrient that prevents lipid peroxidation. The objective of the study was to investigate long-term effects of selenium supplementation on plasma lipid profile in rats. Design: To investigate the effect of this micronutrient on plasma lipid levels, adult rats supplemented with selenium (20 mu g/Kg body weight) for 16 weeks were studied. Plasma selenium levels were found to be 167.9 +/- 3.8 mu g/l and 193.9 +/- 3.8 mu g/l in control and selenium treated rats, respectively. Results: Selenium supplementation significantly lowered the concentrations of plasma triglycerides by 21% and low density lipoprotein cholesterol (LDL-cho) by 42%. Also, the ratio of LDL-cho to either high density lipoprotein cholesterol (HDL-cho) or to total-cho was significantly lowered. On the ether hand, selenium did not influence HDL-cho and total-cho concentrations although their relative ratio to each other was significantly increased (p<0.001). Plasma selenium levels in the examined rats were negatively correlated with plasma triglycerides (r = -0.3479) and LDL-cho (r = -0.3177) concentrations. Conclusions: Therefore, the food supplementation with selenium might be beneficial in improving lipid profile, the major risk factor for coronary heart disease (CHD).