Double-chambered right ventricle is an uncommon congenital anomaly consisting of obstruction of the trabecular zone of the ventricle by an elevated, hypertrophied moderator band, with or without additional muscle bundles(s). During an 18 month period (August 1984 to February 1986) 12 patients underwent repair of double-chambered right ventricle. Their ages ranged from 13 months to 12 years (mean 4.4 years). Associated lesions were ventricular septal defect in 11 patients (three closed spontaneously), atrial septal defect in two, left superior vena cava in three, aortic valve prolapse in one, and mild subaortic stenosis in two. Right ventricular outflow tract gradients were from 30 to 165 mm Hg (mean 77.2 ± 37.3 mm Hg). The initial six patients (Group 1) were treated in the 'classical' manner with a right ventriculotomy for muscle resection and ventricular septal defect closure (4/6). All patients survived. Five of the six required pharmacologic support for signs of mild to moderate right ventricular failure. The right ventricular outflow tract gradient postoperatively was 0 mm Hg in five patients and 25 mm Hg in one patient. Oxygen saturations were checked in the right atrium and pulmonary artery in all six patients, and one patient had a step-up of more than 10%. In the next six patients (Group 2) a previously unreported right atrial-pulmonary artery approach was used to avoid a ventriculotomy. The right ventricular outflow tract gradient was 0 mm Hg in five patients and 5 mm Hg in the sixth. A ventricular septal defect was closed in four of the six patients. There were no deaths, and no patient required inotropic support. Follow-up has been from 2 to 20 months. There have been no late deaths, and all patients are asymptomatic. One patient in Group 1 still has signs of a residual ventricular septal defect at 1 year. No patient has echocardiographic evidence of right ventricular outflow tract obstruction. All patients have remained in sinus rhythm with right bundle branch block. No patient has been recatheterized. Repair of double-chambered right ventricle is easily performed without a ventriculotomy. The atrial exposure of the ventricular septal defect is excellent. The muscle bundle(s) can be visualized easily through an initial transverse pulmonay arteriotomy with completion of resection through the tricuspid valve.