The effect of n-3 fatty acids in 11 men with hypertriglyceridaemia was investigated. The subjects were given daily supplements with three different doses of n-3 fatty acids for 8-week periods. The supplements given were 2, 4 and 9 g of n-3 fatty acids/day, respectively. Total cholesterol, triglycerides and the ratio of total cholesterol to HDL-cholesterol significantly decreased with all three doses in a dose-dependent way. HDL-cholesterol increased in a dose-dependent fashion, while apolipoproteins A1 and B were unaltered by the supplements apart from a small increase in apolipoprotein A1 after the lowest dose of n-3 fatty acids. The greatest effect was observed after 2 g of n-3 fatty acids/day.