Since June 1989, 18 patients with atrioventricular discordant anomalies under 15 years of age underwent anatomic correction, or double switch operation, with 2 hospital deaths (11%). Ages ranged from 1 year 4 months to 12 years (mean 7.2 years) and body weights ranged from 7.1 to 32.5 kg (mean 20.1 kg) at operation. Visceral situs was solitus in 12 and inversus in 6. Ventriculoarterial connection was discordant in 4 and double-outlet in 14. All had associated congenital cardiac anomalies consisting of ventricular septal defect in 17, atrial septal defect in 9, pulmonary atresia in 10, pulmonary stenosis in 6, systemic tricuspid regurgitation in 9, mitral regurgitation in 6, bilateral superior venae cavae in 6, patent ductus arteriosus in 6, Wolff-Parkinson-White syndrome in 2, and congenital atrioventricular block in 1. Previous palliation had been performed 19 times in 11 patients including systemic-pulmonary shunts in 10 patients and pulmonary banding in 1 patient. Anatomic correction consisted in the Mustard procedure in 12 or the Senning procedure in 6 at the atrial level and in external conduit repair in 14, arterial switch operations in 3, or direct anastomosis between the pulmonary artery and right ventricle in 1 at the ventriculoarterial level. The arterial switch operation was indicated in patients with a normal pulmonary valve, and external conduit repair was indicated for patients with pulmonic stenosis or atresia. Anatomic right ventricular end-diastolic volume showed significant reduction from 122.2% +/- 46.3% of normal to 78.8% +/- 24.0%, mainly owing to unloading of the ventricle after the operation (p < 0.0003). Right ventricular ejection fraction remained unchanged (56% +/- 8% to 56% +/- 6%). Anatomic left ventricular end-diastolic volume and left ventricular ejection fraction remained unchanged before and after the operation: volume 134.6% +/- 50.0% of normal to 127.3% +/- 32.8% and ejection fraction from 61% +/- 8% to 56% +/- 8%. Cardiac index averaged 3.1 +/- 0.5 L/min per square meter after the operation. The double switch operation is best indicated in patients with atrioventricular discordance associated with systemic tricuspid regurgitation and/or with poor systemic right ventricular function.