Surgical isolation of the entire right ventricular free-wall was performed in ten dogs to evaluate the effects of the procedure on a variety of electrophysiologic measurements. Complete surgical isolation of the right ventricle was confirmed by determining that right ventricular electrical activity was not conducted to the remainder of the heart and that electrical activity in the atria or left ventricle did not conduct to the right ventricle. Right ventricular isolation caused no change in right ventricular or left ventricular pacing thresholds, in effective refractory periods of the right ventricle or left ventricle, or in right ventricular free-wall conduction time. Moreover, the normal conduction time from the right atrium to the left ventricle was 139 ± 5 msec (mean ± standard error) preoperatively and 135 ± 5 msec postoperatively (p is not significant), showing that atrial-to-left ventricular synchrony was unaltered by isolation of the right ventricle. However, following isolation, the right ventricle could not be electrically fibrillated in 9 of 10 animals, a finding that may have important implications in the future development of surgical procedures to control chronic, life-threatening ventricular tachyarrhythmias.