Cor triatriatum is a relatively rare cardiac anomaly, whose major feature is a fenestrated membrane separating an upper common pulmonary venous chamber from a lower true left atrial cavity. Interatrial communications may be present between the right atrium and the common pulmonary venous chamber or the true left atrium. From April 1981 to April 1992, 24 patients with cor triatriatum were treated at Seoul National University Hospital. Ages ranged from 1 month to 24 years with mean of 7.4 years. Twenty patients had interatrial communications through a patent foramen ovale, primum or secundum defect of the atrial septum. Four had no interatrial communications. Fourteen patients had associated anomalies; partial anomalous pulmonary venous connection in 3, total anomalous pulmonary venous connection in 2, persistent left superior vena cava in 3, and other anomalies in 6 patients. Surgical corrections were performed through right atriotomy in 18 patients, left atriotomy in 4, and both atriotomy in 2. Three patients [12.5%] died early after operation; two of them were associated with single ventricle. Six out of 21 survivors [28.6%] experienced complications; recurrent pneumonia, pulmonary embolism, ischemic encephalopathy, diaphragmatic palsy and tachyarrhythmias. At the time of follow up, all survivors, except one, were in functional class I. Surgical correction of cor triatriatum restored normal hemodynamic status with relatively low operative mortality, especially in patients not complicated with severe anomalies. This report summarizes the clinical diagnosis, associated anomalies, interatrial communications, surgical approach and late result of 24 patients underwent surgical corrections in our hospital.