Diagnosis and successful surgical repair of cor triatriatum, associated with anomalous pulmonary/systemic venous connection in a 6-month-old infant, is described. Follow-up at 2 years revealed no abnormalities. The clinical findings, hemodynamics, and surgical treatment are discussed, together with a review of the literature. This is a rare, life-threatening situation presenting significant diagnostic difficulties in infancy. It is, however, amenable to surgery provided that an early diagnosis is achieved.