Drainage of the inferior vena cava into the left atrium during surgery for closure of an atrial septal defect is a rare complication. More common in low situated defects, it was more frequent when this type of surgery was performed without cardiopulmonary bypass. This diagnosis was made in a 45 year old woman with cyanosis operated 28 years previously. The right-to-left shunt was demonstrated by the hyperoxia test and confirmed by perfusion pulmonary scintigraphy and contrast echocardiography but only when the contrast was injected in the inferior vena cava territory, and by angiography. The surgeon confirmed the abnormality, closed the interatrial septum and reconnected the inferior vena cava to the right atrium.