Atrial septal defect (ASD) frequently gives rise to a distinctive pattern of high, peaked jugular V waves which often exceed the A waves in height. Both the X and Y descents are relatively deep. Of 27 patients with ASD and normal pulmonary vascular resistance, 11 (41%) showed a pattern which, in itself, was sufficiently characteristic to be virtually diagnostic of ASD. This pattern generally indicates a fairly large left-to-right shunt and is lost when pulmonary hypertension complicates the picture. With rare exceptions, such a venous pulse was not seen in normal individuals and in patients without ASD.