30 years ago the observation of a lower incidence of cardiovascular diseases in Inuits (Eskimos) was related to the higher fish consumption when compared to the residual Danish population. Clinical studies confirmed this finding. It was explained by the higher content of polyunsaturated fatty acids (PUFA) in fish, especially of omega-3 PUFAs. Experimental studies in cell cultures and also in animals with and without infarction models verified the anti-arrhythmic effect of omega-3 PUFAs among other possible contributing factors when compared to other fatty acids. In clinical studies a significant reduction (ca. 40%) of sudden cardiac deaths (SCD) could be found in patients after an acute myocardial infarction (AMI), if they were treated with at least 1 g omega-3 PUFAs daily, either by consumption of fish twice weekly or of a highly purified preparation omega-3 PUFAs in capsules. These findings led to recommendations of the American Heart Association and the European Society of Cardiology (ESC) to a higher fish consumption and/or the daily intake of 1 g O-3 PUFAs for primary and especially for secondary prevention of cardiovascular diseases. The much fewer side-effects, and the standardised dosage on one hand and the negative effect of the sometimes higher mercury content of fish make the intake of omega-3 PUFAs as capsules the better choice.