The potential role of omega-3 PUFA intake in the prevention of coronary heart disease is supported by studies among Greenland Eskimos, the Japanese, the Dutch, and data from the Western Electric Study. The low incidence of coronary heart disease among Eskimos and Japanese populations has been attributed to high dietary intake of fish oils. In addition, a large cohort study from the Netherlands found an inverse relationship between regular fish consumption and coronary heart disease mortality. Mortality from coronary heart disease was increased 2.5 fold among persons who did not consume fish compared to those who consumed at least 30 grams/day or the equivalent of 1-2 fish meals per week. There was no evidence that increasing fish intake above 30 grams per day provided additional benefit; moderate intake had the greatest effect on coronary heart disease mortality. Dietary omega-3 PUFA intake, though modest, was also inversely related to coronary heart disease mortality. Analysis of dietary data from the Western Electric Study cohort also suggested an inverse relation between fish consumption and coronary heart disease mortality. In contrast, cohort studies from Hawaii and Norway observed no relation between fish consumption and coronary heart disease. However, fish consumption was higher in these populations and there were few individuals who did not consume fish. Prior to the present study, there had been no studies of the relation between dietary fish intake and the risk of primary cardiac arrest.