Original Article Background: Excellent surgical results have been reported after repair of complete atrioventricular septal defects (CAVSD); however, 5% to 10% require reoperation. We examine causes leading to reoperation and evaluate long-term outcome. Methods: Between 1972 and 2007, 50 patients (26 male) underwent reoperation at our institution after initial repair of CAVSD (median interval, 15 months; range, 3 days to 29 years). Median age at first reoperation was 4.5 years (range, 53 days to 38 years). Indications for first reoperation included left atrioventricular valve (LAVV) regurgitation in 41 patients, subaortic stenosis in 5, and LAVV stenosis, residual atrial septal defect (ASD), pulmonary artery (PA) stenosis, and aortic coarctation in 1 each. Results: The first reoperation included LAVV repair in 21 patients and replacement in 21, modified Konno procedure in 3, septal myectomy in 2, and PA reconstruction, coarctation repair, and ASD re-repair in 1 each. After LAVV repair (n = 21) 5 patients required a second reoperation, and after LAVV replacement (n = 21) 6 patients required a second reoperation. Overall freedom from further reoperation after the first reoperation was 63%, 48%, and 42% at 5, 10, and 15 years, respectively. There were 2 early deaths (4%) after first reoperation, and none after subsequent reoperations. During late follow-up (median 10.7 years, maximum 30 years), actuarial overall survival was 91%, 91%, and 86% at 5, 10, and 15 years, respectively. Conclusions: The most common indication for reoperation after CAVSD repair is LAVV regurgitation. LAVV re-repair offers good durability, and LAVV replacement does not preclude additional reoperations. Long-term survival is very good despite need for multiple reoperations in some. Congenital heart disease,Re-operation,AV Septal Defect 32 33 http://www.iscs.org.ir/journals/vol.2/no.4/51/