The assessment of severity of mitral stenosis is generally based on the mitral valve orifice area as calculated by the Gorlin formula from the invasively-measured pressure gradient and flow across the valve. As an additional reference for evaluating severity, the hemodynamically-determined pressure half-time has been suggested; that is, the time required for the peak gradient across the stenotic valve to drop to one-half of its original value. Since the pressure gradient and the velocity of flow in the region of the stenosis are related to each other as described in the Bernoulli equation and, since the velocity of flow can be analyzed with Doppler echocardiography, the possibility is afforded for noninvasive determination of both the pressure gradient and the pressure half-time. From the Doppler echocardiographically determined pressure half-time, the mitral valve orifice area can be calculated. This study, in a relatively large population of patients with mitral stenosis, was undertaken to compare the pressure half-times obtained from Doppler echocardiography with the valve orifice areas derived from hemodynamic measurement, to analyze the relationship between the two latter parameters and to evaluate the relevance of the newly-developed method. In Doppler echocardiography, the frequency shift of emitted sound reflected from moving blood cells is measured. The velocity of blood flow is proportional to the frequency shift delta f.(ABSTRACT TRUNCATED AT 250 WORDS)