From 1975 to 1990, 90 patients (age, 6 months to 30 years; mean, 9.1 years) underwent operation for defects associated with atrioventricular discordance. Twenty-one had an anatomically abnormal tricuspid (systemic) atrioventricular valve (SAVV) of the following types: Ebstein, 11; straddling, 6; and dysplastic, 4. Sixteen valves were regurgitant: regurgitation was trivial to mild in nine and moderate to severe in seven. Two patients underwent a successful Fontan-type operation. None of the 5 patients with a competent SAVV underwent valve repair or replacement; 1 of these patients died. A ventricular septal defect was closed in 14 and an extracardiac valved conduit was placed in 7. Sixteen had a regurgitant valve: it was replaced in 10 and repaired in 2 (early mortality, 25%). All 4 patients who did not undergo repair or replacement of their regurgitant SAVV died. Two patients died late after repeat replacement. Four other reoperations (closure of a residual ventricular septal defect, SAVV replacement, left ventricle-to-pulmonary artery conduit replacement, and a redo Fontan procedure) were successful. Two patients are lost to follow-up, and 9 have been followed up for them 27 to 156 months (median, 117 months). All were well when last seen. We suggest that an abnormal regurgitant SAVV should be replaced. Alternatively, a "double-switch" procedure that leaves the tricuspid valve in the pulmonary circulation may be used.