n-3 Fatty acids may reduce the incidence of sudden cardiac death, a property potentially related to their activity on myocardial excitability. We carried out a cross-over trial in which 10 coronary patients were treated with n-3 ethyl esters at two different dosages (3 and 6 g day (-1)) for 4 weeks. Plasma fatty acid composition, lipid profile, and heart rate variability (HRV) were analysed. n-3 Fatty acid intake significantly reduced plasma cholesterol and triglyceride levels and decreased the low to high frequency ratio. In addition, significant positive correlations were found between n-3 phospholipid content and HRV indices, thus confirming, in a prospective trial, retrospective data suggesting that an increased HRV may be achieved in coronary patients by exogenous provision of n-3 fatty acids.