The aim of this study was to assess the value and limitations of Doppler echocardiographic measurement of aortic flow in the quantification of aortic regurgitation. Sixty-one patients were examined by Doppler echocardiography within 48 hours of cardiac catheterisation. There were 9 Grade I, 18 Grade II, 18 Grade III and 16 Grade IV angiographic aortic regurgitations. The mean aortic blood flow in angiographic Grades I and II (p less than 0.01). A correlation was observed between Doppler aortic flow and the angiographic grade of regurgitation (r = 0.66, p less than 0.001) and between aortic flow and regurgitant fraction (r = 0.68, p less than 0.001). Aortic flow greater than 10 l/mn identified angiographic Grades III or IV regurgitation with a sensitivity and specificity of 73.5% and 92.5% respectively and a positive and negative predictive values of 92.5% and 73.5% respectively. Aortic regurgitation with a regurgitant fraction greater than 40% was identified by a pulsed Doppler aortic blood flow greater than 10 l/mn with a sensitivity and specificity of 70% and 93% respectively, and positive and negative predictive values of 95% and 61% respectively. The sensitivity of this criterion is relatively poor as some severe aortic regurgitations have aortic flows of less than 10 l/mn: these patients have low outputs because of left ventricular dysfunction which is apparent from measurement of left ventricular fractional shortening.