Ninety-one consecutive patients with aortic regurgitation, either isolated (23 subjects) or associated with other valvular diseases (68 subjects), were studied with pulsed Doppler echocardiography and subsequent aortography, and the results were compared in order to assess the value of the noninvasive technique for a semiquantitative evaluation of the degree of the aortic regurgitation. Both the noninvasive and invasive estimations were graded on a four-point scale. In the long-axis parasternal view, the outflow tract of the left ventricle was divided in four areas going from the aortic valve to the apex. Echo-Doppler grading (from + 1 to +4) was obtained by assessing the area where the abnormal diastolic flow could still be recorded. In the group as a whole, concordant degrees of the aortic insufficiency were obtained in 73 of 91 patients (r = .93; p less than .001); the degree of the aortic regurgitation was overestimated in 8 cases (9%) and underestimated in 10 cases (11%). Most of the discrepancies between the Doppler and the aortographic evaluation were found in patients with intermediate degree (+2, +3) of aortic regurgitation; the degree of discordance was never more than +1 or -1. Correlation between Doppler and aortography was higher in the subjects with pure aortic regurgitation (r = .94, p less than .001) and lower in the subgroup of the subjects with associated mitral stenosis (r = .87, p less than .001). Two-dimensional pulsed Doppler echocardiography is a simple and little time consuming technique that in selected groups of patients can be relied upon for the semiquantitated evaluation of the degree of aortic regurgitation.