The effect of large-dose short-term administration of Max-Epa fish oil on serum lipoproteins in elderly people was studied. 17 elderly (aged 61–96 years) hospital patients were given an isocaloric diet which contained 70–80 ml (14–16 g of eicosapentaenoate) of Max-Epa fish oil for 3 weeks. The concentration of plasma total cholesterol and LDL cholesterol decreased significantly during the diet with fish oil. The levels of plasma VLDL cholesterol, HDL cholesterol and triglycerides decreased slightly (p < 0.05). The concentration of apoprotein A decreased significantly (p < 0.001) during the fish oil diet but the plasma level of apoprotein B did not change significantly. The ratio of apoprotein B to LDL cholesterol increased significantly (p < 0.01) during the period with Max-Epa fish oil. The results show that marked changes in the lipoproteins of the elderly people occur when diet contains large doses of fis