A permanent pacemaker was inserted in eight patients with the long QT syndrome. All had recurrent syncope or seizures, six had documented torsade de pointes and four had aborted sudden death. Among the eight patients, permanent pacing was instituted in three who were unsuccessfully treated with both a beta-adrenergic blocking agent and left cardiothoracic sympathectomy, and in two who proved refractory or intolerant to beta-blockers. Another three patients had pacemaker implantation and long-term beta-blocker therapy because of spontaneous atrioventricular (AV) block in one, aborted sudden death in one and patient preference in one. After pacing (70 to 85 beats/min), there was no significant change in the mean corrected QT interval, but the mean QT interval decreased significantly (534.4 +/- 51.4 to 425.6 +/- 18.9 ms, p less than 0.0001). Over a mean follow-up period of 35.1 +/- 18.9 months, all patients are alive and currently free of syncope. One patient without a history of stress-induced syncope had two syncopal episodes (believed to be due to hyperventilation) while under severe emotional stress, but has been symptom free for the past 5 years. One patient with an atrial demand (AAI) pacemaker developed dizziness due to documented episodes of AV block, but remains asymptomatic after conversion to atrial rate-responsive dual chamber (DDD) pacing. Either atrial or ventricular pacing combined with beta-blocker therapy appears to be effective treatment for a subset of patients with the long QT syndrome, by either preventing episodes of torsade de pointes or alleviating symptoms due to bradycardia from beta-blocker therapy.