n-3 Poliunsaturated Fatty Acids (PUFA) are essential; foods rich in n-3 are fat fish and some vegetal oil. PUFA are precursors of Eicosanoids, involved in the processes of inflammation, thrombosis and immunity. Firstly, observational studies measured reduction of cardiovascular disease (CVD) incidence with greater PUFA dietary intake. Experimental studies discovered antiahrrhytmic, antiatherogenic, antiaggregating and antiinflammatory properties. Retrospective analysis found lower incidence of sudden death (SD) in fish consumers. Randomized, prospective trials after myocardial infarction showed, in people either eating fish or receiving an n-3 PUFA supplement, a reduction of SD, explained by specific effect on membrane ion channels. The lack of results on atherothrombosis do not match with most experimental results, and should better be evaluated in absence of aspirin therapy. Low evidence supports use of n-3 PUFA in angina or revascularization procedures. Recent observations denote positive effect on endothelial function of large and resistance arteries. Actually evidence-based medicine suggest: improve of fish consumption for primary prevention of CVD; n-3 PUFA supplementation for hypertrigliceridemia and secondary prevention of SD after myocardial infarction, which is also cost-effectiveness.