Results of catheter ablation of the atrioventricular (AV) junction in 41 patients were compared with results of cryosurgical ablation in 42 patients. Mean follow-up was 29 months among patients who underwent catheter ablation and 53 months among those who underwent cryosurgical ablation. In both groups complete heart block was produced in most patients (88% in the catheter ablation group, 86% in the cryosurgery group), and similar proportions of patients continued to receive antiarrhythmic drugs (27% in the catheter ablation group, 36% in the cryosurgery group). However, the short-term morbidity rate was significantly lower among patients who underwent catheter ablation (12% vs 42%) (p = 0.004). Long-term mortality and morbidity rates were not significantly different; most deaths were related to underlying cardiopulmonary disease and morbidity to problems with permanent pacemakers. Both catheter ablation and cryosurgical ablation of the AV junction are effective in creating complete AV block and controlling supraventricular tachycardia in medically refractory patients. Because catheter ablation is associated with lower short-term morbidity and avoids the need for a major surgical procedure, it is preferable to cryosurgical ablation of the AV junction when permanent abolition of AV conduction is necessary.