Sixteen patients with either recurrent symptomatic supraventricular tachycardia (SVT) (ten) or ventricular tachycardia (VT) (six) unresponsive to drug treatment underwent insertion of chronic overdrive cardiac pacing devices for arrhythmia control. All patients with SVT followed for longer than 2.5 years required concomitant drug therapy for rhythm control. In addition, one of the ten patients required amiodarone and three required nonpharmacologic therapy (catheter ablation of the atrioventricular junction (one), surgical ablation of the Kent bundle and/or bundle of His (two). In the six patients with VT, only one patient used the device successfully. In the other five patients, either the arrhythmia failed to respond to burst overdrive pacing (three) or overdrive acceleration resulted (two). One death in the latter group was related to induction of rapid VT followed by ventricular fibrillation. Long-term follow-up of patients with paroxysmal SVT shows that virtually all require concomitant drug therapy and may require aggressive medical or surgical procedures for arrhythmia control. Use of ventricular overdrive pacing for those with VT appeared singularly disappointing in that pacing proved either ineffective (three) or resulted in overdrive acceleration (two) in 5/6 patients.