A supra-aortic abnormal flow signal (proximal acceleration) was studied in 62 patients with aortic regurgitation with the use of color Doppler flow mapping. The proximal acceleration signal was detected in 28 of the 62 patients and was shaped like a V or a teardrop. In the 29 patients who underwent aortography, a proximal acceleration signal was observed in all 18 patients with severe and moderate regurgitation and in only one of the 11 patients with mild regurgitation. The sensitivity for the diagnosis of severe regurgitation from the existence of a proximal acceleration signal was 100%, specificity 50%, and predictive accuracy 47%. A close correlation between the area of the proximal acceleration signal and the width of the aortic regurgitant jet signal was observed (r = 0.81). An acceleration area of 45 mm2 or more was observed in eight of the nine patients with severe regurgitation, in four of the nine patients with moderate regurgitation, and in none of the patients with mild regurgitation. Sensitivity for the diagnosis of severe regurgitation from an area of proximal acceleration of more than 45 mm2 was 89%, specificity 80%, and accuracy 67%. These results suggest that evaluation of the area of the supra-aortic abnormal signal may be a useful auxiliary aid in estimating the severity of aortic regurgitation.