This chapter reviews a number of studies which are evaluates the clinical application of operant conditioning techniques in the control of cardiac arrhythmias. It shows that patients can be taught to regulate their cardiac arrhythmias, and that some patients can initiate and maintain this learned behavior outside of the laboratory. Atrial fibrillation is the most common cardiac arrhythmia. The cells in each area of the cardiac conduction system have characteristic rates of depolarization. In either case, the affected tissue depolarizes abnormally late in the cardiac cycle. In one case, pharmacological studies indicated that the cardiac lesion was in the atrioventricular node, and that the ventricular rate probably was mediated by a junctional pacemaker. Ventricular tachycardia is much less common than supraventricular tachycardia, and it is a very serious arrhythmia since it may lead to ventricular fibrillation which is usually fatal.