The cardiovascular benefits of dietary omega-3 polyunsaturated fatty acids (n-3 PUFA) have been actively investigated for nearly 40 years. Beginning with the pioneering studies of Bang and Dyerberg, epidemiological data provide strong evidence for an inverse relationship between fatty fish consumption and cardiac mortality. In contrast to these observational studies, interventional studies using n-3 PUFAs for the secondary prevention of adverse cardiovascular events in patients with heart disease have yielded conflicting results; some studies have reported reduced sudden cardiac death or mortality, while other more recent studies have reported either no effect or an increase in adverse cardiac events. Nevertheless, the American Heart Association and the American College of Cardiology continue to recommend fish oils for the secondary prevention of coronary artery disease. Based in part upon these recommendations, consumer demand for n-3 PUFA products (both nutritional supplements and foods enriched with these lipids) has exploded. In the United States alone, it has been estimated that in 2004, 5-10% of the adult U.S. population were taking a fish oil supplement, with annual sales growth of 40%. In fact, the sales of these products are projected to exceed 7 billion dollars by the end of 2011 (www.marketresearch.com, product reports). Despite the extensive marketing of fish oil products, a scientific consensus on the effects of n-3 PUFA on cardiac rhythm has yet to be reached. It is the purpose of this Research Topic to stimulate a discussion on the putative benefits of n-3 PUFAs on cardiac rhythm. Authors are invited to submit clinical, translational, or experimental research articles, reviews, and hypotheses that address the actions of n-3 PUFA (positive, negative, or neutral) on cardiac rhythm and cardiac electrophysiology. Studies that evaluate the effects of n-3 PUFA on myocyte electrical properties, atrial fibrillation, ventricular fibrillation, and heart rate variability are particularly welcome.