Twenty-seven patients with moderate or severe mitral stenosis (MS) were studied by cardiac catheterization and angiography, 2-dimensional (2-D) echocardiography and Doppler echocardiography to assess the ability of Doppler ultrasound to accurately measure mitral valve orifice area and to assess whether mitral regurgitation (MR) affected the calculation. Mitral valve area by Doppler was determined by the pressure half time method. There were good correlation between 2-D & Doppler echocardiography (r=0.84) and between cardiac catheterization & Doppler echocardiography (r=0.83) regardless of the presence of MR. It is concluded that the Doppler echocardiography provides a simple, accurate, useful noninvasive method for the estimation of mitral valve area in patients with MS even in the presence of complicating MR.