The effects of consuming oils providing alpha-linolenic (ALA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids were studied in healthy volunteers. A blunted increase in plasma triglyceride was observed in subjects given a test meal containing fish oil compared with olive oil; cholesterol concentrations were not increased; increases in EPA and DHA were seen in all lipid fractions. In longer term supplementation studies, ALA increased EPA, but not DHA in plasma phospholipids; preformed EPA was more effective. The proportion of EPA in platelet lipids increased in a dose dependent manner. EPA or DHA, but not ALA, decreased plasma triglyceride and VLDL cholesterol concentrations. Supplements containing DHA increased HDL and HDL2 cholesterol and LDL apoB. Total cholesterol and LDL cholesterol concentrations were unaltered.