We aimed to evaluate surgical repair of atrioventricular valve regurgitation in patients with functional single ventricle.The medical records of 65 consecutive patients with functional single ventricle who underwent atrioventricular valve repair between January 1999 and October 2008 were reviewed retrospectively. Their characteristics were as follows: median age, 9.5 months; median weight, 6.0 kg; atrial isomerism, 31 patients; and hypoplastic left heart syndrome, 12 patients. Regurgitation was repaired at the palliative, Glenn, and Fontan stage in 21, 29, and 15 patients, respectively.The overall survival was 79% and 70% at 1 and 5 years, respectively. The risk factors for mortality were age less than 3 months (P < .001), body weight less than 4 kg (P < .001), hypoplastic left heart syndrome (P = .001), concomitant Norwood (P < .001), and the palliative stage (P = .004) on the univariate analysis, and body weight less than 4 kg (P = .010, hazard ratio, 9.8; 95% confidence interval, 1.7-55.6) on the multivariate analysis. Twenty patients underwent reoperation (repairs in 15; replacements in 5), and freedom from reoperation at 1 and 5 years was 69% and 57%, respectively. Concomitant systemic-to-pulmonary shunt (P = .040) was a risk factor for reoperation on the univariate analysis. Of the 48 survivors, 38 underwent Fontan completion, 7 underwent the Glenn procedure, and 3 are awaiting the Glenn procedure.The midterm results of atrioventricular valve repair in patients with functional single ventricle were favorable; however, young and small patients, especially those with hypoplastic left heart syndrome, still had poor outcomes.