In Eskimos coronary heart disease is a rarity. This can partly be explained by their favorable plasma lipid levels. An additional factor seems, however, to be that in Eskimo food polyunsaturated fatty acids of the ω-3 series replace those of the ω-6 series. C20:5, ω-3 can be converted by the vessel wall to an antiaggregatory substance, whereas it has no proaggregatory effect on platelets. Consistent with these findings Eskimos were found to have a nearly 2-fold longer bleeding time than Danes. Platelet aggregability, too, was merkedly depressed when exposing platelets from Eskimos to ADP and collag