Cor triatriatum represents <0.1% of all congenital cardiac malformations. Symptoms in patients with cor triatriatum are related to pulmonary venous obstruction and pressure loading of the right side of the heart. The aim of this study was to describe our institutional experience with repair of cor triatriatum. From June 1963 to June 2010, 65 patients underwent repair at a median age of 7.2 months (range 2 days to 47.6 years). Among these patients, 49 (75%) had associated congenital heart defects. Atrial septal defect (n = 29), ventricular septal defect (n = 15), partially or totally anomalous pulmonary venous return (n = 14), mitral valve abnormalities (n = 11), and supravalvar mitral ring (n = 5) were the most common associated defects. Surgical treatment consisted of excision of the membrane, along with additional procedures in 47 patients (72%). Five patients had new postoperative supraventricular arrhythmias. During a median follow-up period of 5.4 years, no patients underwent reintervention for recurrent left atrial obstruction, 7 patients were noted to have minor residual cor triatriatum without obstruction, and 8 patients (including 4 diagnosed before cor triatriatum repair) had pulmonary vein stenosis, 6 of whom underwent intervention for that reason. In conclusion, in this large surgical series of patients who underwent repair of cor triatriatum, there were no cases of significant residual or recurrent cor triatriatum. Although the association between cor triatriatum and pulmonary vein stenosis has been described previously, the relative frequency of this condition in our cohort (>10%, including patients diagnosed before and after cor triatriatum repair) is noteworthy. Abnormalities of the mitral valve and a supravalvar mitral ring were also seen more often than the existing research would suggest, which may be another important consideration in evaluating and following these patients.