Doppler echocardiography is useful for detecting aortic regurgitation (AR). To determine if the presence of retrograde holodiastolic flow in the abdominal aorta can be used to assess the severity of AR, abdominal aortic flow velocity was examined by pulsed Doppler echocardiography in 33 patients with AR and 10 patients without AR confirmed by aortography, and in 15 normal subjects. Among the 33 patients with AR, 15 had mitral regurgitation, 11 had mitral stenosis, 8 had aortic stenosis, 5 had prosthetic mitral valves, 4 had prosthetic aortic valves and 2 had aorticopulmonary shunts. No retrograde holodiastolic flow was found in the abdominal aorta of 15 normal subjects or 10 patients without AR. Of the 22 patients with 1+ or 2+ AR independently determined by injection of iodinated contrast into the aortic root, 21 did not have retrograde holodiastolic abdominal aortic flow, whereas all 11 patients with 3+ or 4+ AR had retrograde holodiastolic flow in the abdominal aorta. One patient with 1+ AR and a left-to-right aorticopulmonary shunt had retrograde holodiastolic flow in the abdominal aorta. The finding of holodiastolic retrograde flow in the abdominal aorta is useful for distinguishing patients with severe AR from those with mild or absent AR. Moreover, the method is easy to perform and results appear to be independent of the presence of other cardiac diseases except significant aorticopulmonary shunt.