Twenty-four patients with aortic stenosis and 22 with aortic insufficiency were evaluated using continuous wave Doppler echocardiography (echo). Doppler echo studies were performed 48 hours before cardiac catheterization. Fifteen normal subjects served as controls. Peak velocity in the ascending aorta in aortic stenosis ranged from 2.0 to 6.0 m/sec with a mean of 3.7 m/sec, and this was significantly increased over the normal controls (mean 1.1 m/sec: 0.7-1.4 m/sec). Using the simplified Bernoulli equation (P = 4 V2, P: peak pressure gradient, V: peak flow velocity), the peak pressure gradient across the aortic valve was measured from the peak velocity in patients with aortic stenosis. The results (Y) correlated well with the peak-to-peak pressure gradient (X) between the left ventricular pressure and aortic pressure as obtained by cardiac catheterization (Y = 1.1 X +2.5, r = 0.83). Aortic regurgitation was detected by continuous wave Doppler echo in all patients with aortic insufficiency, but in only half of the patients the peak velocity could be measured (3.8 +/- 0.3 m/sec, mean +/- SD). In the remaining patients, it was difficult to measure the peak velocity, but it seemed to be greater than 3.0 m/sec. On the simultaneous recordings of the gradient between aortic and left ventricular pressures and continuous wave Doppler echo in patients with aortic regurgitation, the shape and pattern of the pressure gradient during diastole were similar to those of continuous wave Doppler echo. We conclude that continuous wave Doppler echo is a very sensitive method for diagnosing aortic stenosis and regurgitation, and it provides a quantitative assessment of the severity of aortic stenosis.