Sudden cardiac death (SCD) is a major cause of mortality in Western countries. Furthermore, SCD is often the first manifestation of coronary artery disease, making it difficult to prevent. Heart rate variability (HRV), which can be determined by extended recording of the heart rate by 24-h Holter monitoring, has been shown to be one of the best predictors of the risk of SCD. There is increasing evidence from animal experiments and clinical trials in humans that n-3 fatty acids reduce the risk of SCD. We have studied the effect of n-3 fatty acids on HRV and present data clearly showing that n-3 fatty acids increase HRV. This adds further to the hypothesis that an increased intake of n-3 fatty acids may reduce the risk of SCD.