Increased platelet functions have been associated with enhanced arachidonic acid (AA) metabolism in diabetics and elderly people. We investigated these parameters in both groups after feeding low doses of pure eicosapentaenoic acid (EPA). After such an intake, platelet aggregation induced by various agonists was decreased whereas the oxygenated metabolism of endogenous AA was not substantially altered, and the fatty acid composition of plasma and platelet lipid pools did not change. In the most recent study, the measurement of vitamin E revealed that although its level in plasma was not modified, it was increased in platelets after EPA intake. It is concluded that small amounts of EPA intake do not reduce platelet aggregation in competing with AA metabolism but rather in depressing the peroxide tone of the cell.