It has been shown in animals and probably in humans that the n-3 polyunsaturated fatty acids are antiarrhythmic. We report recent studies on the mechanism(s) by which the polyunsaturated fatty acids exert their antiarrhythmic effects. The polyunsaturated fatty acids stabilize the electrical activity of isolated cardiac myocytes by inhibiting sarcolemmal ion channels, so that a stronger electrical stimulus is then required to elicit an action potential and a contraction of the myocyte. This appears at present to be the probable major antiarrhythmic mechanism of the polyunsaturated fatty acids.