Abstract One hundred twenty-five patients undergoing surgical correction of total anomalous pulmonary venous return were studied. The overall mortality was 37% and was related to age at the time operation was required. Mortality was 57% during the first year of life, 29% in patients between 13 and 24 months, and 15% in those between 2 and 10 years; no deaths occurred in those over 10 years. Mortality was highest in patients with infracardiac lesions (62%), and lowest in those with cardiac defects (30%). The major cause of death was pulmonary edema, and survival was closely related to the degree of increased pulmonary vascular resistance. Surgical treatment should be delayed until at least 6 months of age, but the development of congestive heart failure may necessitate earlier operation.