gamma-Linolenic acid [GLA, 18:3(n-6)], eicosapentaenoic acid [EPA, 20:5(n-3)] and docosahexaenoic acid [DHA, 22:6(n-3)] have been reported to prevent cardiovascular diseases. However, they are highly unsaturated and therefore more sensitive to oxidation damage. We investigated the effects of a diet rich in these polyunsaturated fatty acids (PUFA) on blood pressure, plasma and lipoprotein lipid concentrations, total antioxidant status, lipid peroxidation and platelet function in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY). Five-week-old SHR and WKY rats were fed for 10 wk either a diet containing Isio 4 oil or a diet rich in GLA, EPA and DHA (5.65, 6.39 and 4.94 g/kg dry diet, respectively). The total antioxidant status was assayed by monitoring the rate of free radical-induced hemolysis. VLDL-LDL sensitivity to copper-induced lipid peroxidation was determined as the production of thiobarbituric acid reactive substances. After dietary PUFA supplementation, a significant decrease in blood pressure of SHR rats (-20 mm Hg) was observed and the total antioxidant status was enhanced. VLDL-LDL resistance to copper-induced peroxidation was increased in both strains. The PUFA supplementation did not change platelet maximum aggregation in SHR rats, but it decreased the aggregation speed. In hypertensive rats, GLA + EPA + DHA supplementation lowers blood pressure, enhances total anti-oxidant status and resistance to lipid peroxidation, diminishes platelet aggregation speed and lowers plasma lipid concentrations. Thus, it enhances protection against cardiovascular diseases. Therefore, nutritional recommendations for cardiovascular disease prevention should take into account the pharmacologic properties of GLA, EPA and DHA.