The radio- and angiocardiographic characteristics of 19 infants with an interrupted aortic arch were reviewed. There were three with type A (distal to the left subclavian artery), 15 with type B (between the left carotid and subclavian arteries), and one with type C (between the innominate and left carotid arteries). Associated cardiovascular anomalies were numerous, a ventricular septal defect (19/19) and a patent ductus arterisous (18/19) being the most common. Plain film signs of aortic interruption were nonspecific. Left ventriculography using angled oblique views was diagnostic of the interruption and most other abnormalities. The constant presence of a ventricular septal defect and frequent occurrence of left ventricular outflow obstruction in these infants lends support to the theory that decreased flow in the fetal ascending aorta predisposes to interruption of the aortic arch.