The low incidence of myocardial infarction in Greenland Eskimos may be due to their intake of marine food with a high content of n-3 polyunsaturated fatty acids (PUFAs). In Eskimos the platelet count is lowered, the platelet aggregation is inhibited, the bleeding time is prolonged and the ratio between proaggregatory thromboxanes and anti-aggregatory prostacyclins is decreased, when compared to age- and sex-matched Danes. In this review, studies evaluating the effect of a fish diet or fish-oil supplementation on human platelet function are summarized. Most studies have demonstrated that supplementation with n-3 PUFAs can cause inhibition of platelet behaviour. The optimal dose of n-3 PUFAs and the patient groups most likely to profit from supplementation need to be defined. The safety and the clinical effect of the supplementation should be investigated in long-term studies.