Continuous wave Doppler, colour Doppler, and their combined use were compared for their validity in the semiquantitative evaluation of aortic regurgitation in 80 angiographically proven cases. The diastolic decay slope, as measured from the continuous wave Doppler signal of the aortic regurgitation, correlated well with angiographic data (r = 0.82) and, after classification in three grades, coincided in 78% of all patients. When rated on a three-grade scale the intensity of the aortic regurgitation signal measured by continuous wave Doppler corresponded with invasive data in 82% of patients, and a three-graded maximal width at the base of the colour Doppler regurgitant jet relative to the aortic outflow tract showed agreement in 71%. The best results were obtained by combining continuous wave and colour Doppler indices, which yielded agreement with angiography in 85% of patients. Subdivision of the patient group into those with pure aortic regurgitation and those with combined aortic lesions revealed less accurate gradings with both Doppler methods in the presence of aortic stenosis.