Dietary alpha-linolenic acid (ALA) can be converted to long-chain (n-3) PUFA in humans and may potentially reproduce the beneficial effects of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids on risk factors for coronary heart disease (CHD). This study compared the effects of increased intakes of ALA with those of dietary EPA and DHA on blood coagulation and fibrinolytic factors in fasting subjects. A placebo-controlled, parallel study was conducted in 150 moderately hyperlipidemic subjects, age 25-72 y. Subjects were randomly assigned to one of five interventions and consumed a total intake of 0.8 or 1.7g/d EPA+DHA, 4.5 or 9.5g/d ALA or control (linoleic acid; LA) for 6 mo. Fatty acids were incorporated into 25 g of fat spread, which replaced the subject's normal spread and three capsules. Long-term supplementation with either dietary EPA+DHA or estimated biologically equivalent amounts of ALA did not affect factors VIIa, VIIc, VIIag, XIIa, XIIag, fibrinogen concentrations, plasminogen activator inhibitor-1 or tissue plasminogen activator activity compared with the control. (n-3) PUFA of plant or marine origin do not differ from one another or from LA in their effect on a range of blood coagulation and fibrinolytic factors.