In a double-blind, crossover, placebo-controlled study the effects of four weeks' treatment with 4.55 g/day of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on BP and serum lipids were assessed in 18 males with hypertension (WHO stage I-II). At the end of the double-blind phase, eight patients on placebo (olive oil) and ten patients on fish oil treatment were given nifedipine 20 mg twice daily added to their regimens for four weeks. Four weeks' fish oil treatment slightly reduced BP values; however, compared with placebo no changes were found. VLDL-cholesterol and triglycerides were significantly reduced by 24%, whereas total and LDL-cholesterol remained unchanged. Placebo did not change BP and lipid values. When nifedipine was added to fish oil/placebo, BP in the two groups was reduced to almost the same extent. When nifedipine was added to fish oil, total cholesterol was significantly reduced by 12% in comparison with baseline value and LDL-cholesterol was reduced by 15%, albeit insignificantly. Placebo plus nifedipine was lipid neutral. A significant correlation was found between the nifedipine-induced changes in supine mean arterial pressure and total, LDL- and VLDL-cholesterol, respectively, in those patients with and without fish oil treatment. In conclusion, the combined administration of fish oil and nifedipine possesses favourable antihypertensive and metabolic properties in hypertensive males with elevated lipid levels.