Abstract Several long term epidemiological surveys and some direct intervention trials suggest that long chain omega-3 PUFA rich diets reduce mortality from coronary heart disease. There is evidence that this is due primarily to a reduction in mortality from sustained ventricular fibrillation, cardiac arrhythmia and sudden death. A series of studies utilising the small non-human primate marmoset monkey have shown that diets enriched with fish oil enhance left ventricular ejection fraction and peak emptying rate, elevate the ventricular fibrillation threshold and reduce mortality during ischaemia or catecholamine induced stress. Analysis reveals that there is considerable accumulation of docosahexaenoic acid in the myocardial muscles of these non-human primates and it is suggested that this is a major factor in the decreased susceptibility of the myocardium to develop ventricular fibrillation. A recent experiment in rats subjected to ligation of a major coronary artery supports this suggestion.