Coronary heart disease (CHD) mortality was registered in an inland and a coastal community in Northern Norway. Subgroups of healthy males from the communities were investigated further. The daily consumption of fish in the coastal and inland areas was 132.4 g and 55.1 g respectively, and the intake of eicosapentaenoic acid was 0.9 g and 0.25 g. The content of n-3 polyunsaturated fatty acids in platelet phospholipids and primary bleeding time were similar in the two groups. Linoleic acid was lower and saturated fatty acids were higher in phospholipids in men from the coastal area. Collagen-induced platelet aggregation was increased and serum triglyceride concentration was higher in men from the coastal area. CHD mortality during a 10-year period was higher in the coastal area for both sexes. This may be associated with differences in serum triglyceride levels and platelet fatty acid composition. This study indicates that a high consumption of lean fish is not sufficient to induce changes in blood lipids and platelet function associated with low CHD mortality and it does not seem to prevent high CHD mortality.