Twenty-five patients with the preexcitation syndrome underwent operation for ablation of an accessory pathway. The patients were young (mean age 28.1 years) and 20% had congenital heart disease. In 24, markedly symptomatic refractory supraventricular tachycardia had been present for a mean of 12.6 years. The accessory pathway was right or left ventricular free wall in 22 patients and septal in 3 patients. Operation resulted in persistent ablation of the pathway in 80% of the patients. There was no perioperative mortality and no persistent complete heart block. During a mean follow-up of 15.6 months, 83.3% of patients with a preoperative history of supraventricular tachycardia had no recurrence of the arrhythmia. Two patients (8.3%) had macro-reentry paroxysmal supraventricular tachycardia related to a persistently functioning bypass tract. The remaining two patients had supraventricular tachycardia unrelated to a functioning accessory pathway. We conclude that the surgical treatment of patients with preexcitation syndrome (Wolff-Parkinson-White) is safe and effective. It should be considered (1) in patients who are markedly symptomatic with refractory supraventricular tachycardia, (2) in those who have the potential for sudden cardiac death, (3) in younger patients with symptomatic tachycardia in whom there is concern about the long-term effects of antidysrhythmic treatment, and (4) in patients with tachycardia who are undergoing cardiac surgery for repair of associated conditions.