Background Outcome of surgical correction of atrioventricular septal defects (AVSD) still varies despite enhanced results. We reviewed our 30-year experience with AVSD repair and identified risk factors for mortality and reoperation. Methods Between 1975 and 2006, 312 patients underwent surgery for complete AVSD (n = 209; 67.0%), partial AVSD (n = 76; 24.4%), or intermediate AVSD (n = 27; 8.6%). Mean age was 2.4 ± 3.9 years; 142 patients (45.5%) were younger than 6 months. Follow-up was 99.0% complete. Results There were 26 in-hospital deaths (8.3%) and 6 late deaths (2.1% of 283). Estimated overall survival for the total study population was 91.3%, 90.6%, and 88.6% at 1, 5, and 15 years, respectively. In the multivariable logistic regression analysis, surgical era 1975 to 1995 ( p < 0.001) and younger age ( p = 0.004) were found to be independent risk factors for early mortality, whereas preoperative AV valve insufficiency showed a tendency toward statistical significance ( p = 0.052). Of the hospital survivors, 43 patients required a late reoperation. Estimated freedom from late reoperation was 96.4%, 89.3%, and 81.8% at 1, 5, and 15 years, respectively. Multivariable Cox regression analysis showed associated cardiovascular anomalies ( p < 0.001), left AV valve dysplasia ( p < 0.001), and absence of cleft closure ( p = 0.003) to be independent risk factors for late reoperation. Conclusions AVSD repair can be accomplished with good long-term results. Early surgical era, associated cardiovascular anomalies, left AV valve dysplasia, and absence of cleft closure negatively influence survival and risk of reoperation.