Multiple cardiac arrhythmias have been noted following cardiac transplantation, and these observations suggest that denervation does not protect the heart from the initiation of arrhythmias. The sequential electrocardiograms of 45 of 47 cardiac transplant patients at Stanford were reviewed. Currently, 16 patients are alive for periods up to 40 months post-transplantation. Atrial arrhythmias were noted in 72% of patients, and were usually associated with acute rejection episodes. Ventricular premature beats were detected in 57% of patients post-transplantation. Two documented episodes of ventricular fibrillation have occurred during severe acute rejection episodes. Two long-term survivors died suddenly of a presumed ventricular arrhythmia, and at autopsy both showed severe coronary atherosclerosis. This experience suggests that innervation is not necessary in the genesis of cardiac arrhythmias in the transplanted human heart.