This article describes 18 patients with drug-resistant ventricular bigeminy and other forms of complex ventricular ectopy (allorhythmias) associated with recurrent syncope. Particular emphasis is placed on the electrophysiologic methods used to characterize the basis of these arrhythmias and to accomplish isochronous mapping to identify their site of origin. A malignant course of drug-resistant bigeminy in combination with other rhythm disorders was accepted as indications for surgical intervention. Cryosurgery was the method used most frequently for the ablation of arrhythmogenic myocardium. All 18 patients underwent postoperative electrophysiologic studies and Holter monitoring to determine the efficacy of the operation. Fifteen of the 18 patients were cured of their symptomatic arrhythmia. Thus surgical intervention is an effective method for the treatment of patients with symptomatic, drug-resistant ventricular allorhythmias.