Objective. The objective of this study was to review our current experience using a combination of beta-adrenergic blocking agents and long-term cardiac pacing to treat patients with the idiopathic long QT syndrome. Background. Patients with the idiopathic long QT syndrome are at high risk for sudden cardiac death. Before combination therapy, 20 of the 21 study patients experienced either cardiac arrest (n = 8) or syncope (n = 18) and 11 had documented polymorphous ventricular tachycardia. Nine of these patients had not responded to isolated beta-blocker therapy and five had not responded to isolated left cervicothoracic sympathectomy. Method. All patients were treated with combined beta-blocker therapy and long-term cardiac pacing at a rate designed to normalize the QT interval. Results. Cardiac pacing at rates of 70 to 125 beats/min resulted in shortening of the QT and corrected QT (QTc) intervals from 517 ± 78 and 541 ± 62 ms to 404 ± 37 and 479 ± 41 ms, respectively. The mean follow-up interval after institution of pacing was 55 ± 45 months. The only sudden death occurred in a patient who had discontinued beta-blocker therapy. Syncope occurred in four patients, two of whom had interrupted pacemaker function due to lead fracture. Pacemaker problems, partly attributable to the specific rate required for QT interval shortening and to avoidance of T wave sensing, were relatively common. No patient who continued the combination therapy died, but 10% of these patients had a recurrence of symptoms. Conclusions. Combination therapy with a beta-blocker and cardiac pacing appears to be a highly effective primary therapy for symptomatic patients with the long QT syndrome and to provide excellent adjunctive therapy for patients who require insertion of an automatic internal defibrillator.