Pulmonary venous atrial stenosis developed after a modified Senning procedure in an infant with transposition of the great arteries. The pulmonary venous atrium was surgically revised, but the obstruction recurred. The stenosis was then enlarged by percutaneous balloon catheter dilatation. There was an immediate haemodynamic and echocardiographic improvement. Clinical and echocardiographic improvement persisted nine months after dilatation. The procedure was complicated by staphylococcal endarteritis.