Aortic flow patterns were analyzed using two-dimensional Doppler echocardiography for 15 patients with patent ductus arteriosus, seven with ruptured aneurysms of the sinus of Valsalva, two with coronary artery fistulae and for 22 healthy persons, with special reference to diastolic flow patterns. The conclusions were as follows: In healthy subjects, there was a tiny and transient reversed flow signal in early diastole followed by a slow and sustained diastolic forward flow signal. The velocity of the diastolic forward flow was slower and the duration was shorter in the lower abdominal aorta than in the upper portion. In patients with shunts from the aorta to the right-sided chambers, the early diastolic reverse flow was enhanced, and another reversed flow developed in mid- and late diastole, which was the most evident in the lower portion of the abdominal aorta. The extent of the reversed flow correlated significantly with Qp/Qs by catheterization (r = 0.73). Thus, the abdominal flow patterns in cases with left to right shunts from the aorta to the right-sided chambers of the heart provided information for estimating the size of the shunt volume. In patients with bi-directional shunts, the dominant direction of the shunt during diastole can apparently be determined by analyzing the aortic flow patterns.