Color flow Doppler mapping has become the principal noninvasive method used for the qualitative grading of aortic regurgitation (AR). However, the performance of the color Doppler method in patients with AR accompanying aortic stenosis (AS) has not been studied. We therefore compared results of color Doppler and semiquantitative angiographic grading of AR in 32 patients with AS (mean valve area = 0.7 cm<sup>2</sup>) undergoing supravalvular aortography in the course of cardiac catheterization. Color Doppler demonstrated AR in all 27 patients who had AR by aortography. As expected, neither the maximal jet area nor the jet length discriminated patients by angiographic grade. The best correlation between color Doppler and aortography occurred when the ratio of maximal jet height (JH) to left ventricular outflow tract (LVOT) height was used to grade AR on a scale of 0-4. Four of 5 patients without AR by aortography had either absent or grade 1 AR by color Doppler. Although there was considerable overlap of color Doppler grades in patients with 1+ AR by aortography, grade 3 or 4 AR by color Doppler was always associated with III+ or IV+ AR by aortography. Thus, color Doppler sensitively depicts AR in patients with AS, and the ratio of JH to LVOT height by color Doppler correctly identifies patients with III+ or IV+ AR by aortography. Methods for distinguishing among milder grades require further evaluation.