The first evidence that fish oil fatty acids might have a beneficial effect on coronary heart disease came from the discovery that Greenland Eskimos, who have a diet high in n-3 fatty acids, have a lower mortality from coronary heart disease than do Danes and Americans. Long-chain polyunsaturated fatty acids are essential in our diets and can be classified in 2 groups: n-6 fatty acids found in plant seeds and n-3 fatty acids found in marine vertebrates. Further evidence of n-3 benefits to human health include a 1989 study demonstrating a 29% reduction in fatal cardiac arrhythmias among subjects with a recent myocardial infarction who had been advised to consume fish oil. The GISSI-Prevenzione Trial found a significant reduction in relative reduction of death, cardiac death, nonfatal myocardial infarction, and stroke in subjects consuming n-3 fatty acids. In a recent study, subjects with implanted cardiac defibrillators (ICDs) at high risk for fatal ventricular arrhythmias were randomly assigned to four 1-g capsules of either an ethyl ester concentrate of n-3 fatty acids or olive oil daily for 12 mo. Subjects receiving n-3 who thus had significantly higher levels of eicosapentaenoic acid and docosahexaenoic acid in their red blood cell membranes showed a longer time to first ICD events and had a significantly lower relative risk of having an ICD event or probable event (P = 0.033). These studies demonstrate that fish oil fatty acids have beneficial effects on coronary heart disease.