Patients with mitral stenosis often present during periods of hemodynamic stress such as pregnancy or infections. The Doppler pressure half-time method of mitral valve area (MVA) determination is dependent on the net atrioventricular compliance as well as the peak transmitral gradient. The continuity equation method of MVA determination is based on conservation of mass and may be less sensitive to changes in the hemodynamic state. To test this hypothesis, 17 patients admitted for catheterization with symptomatic mitral stenosis and no more than mild regurgitation underwent Doppler echocardiography at rest and during supine bicycle exercise targeted to an increase in heart rate by 20 to 30 beats/minute. Net atrioventricular compliance was also estimated noninvasively. Cardiac output and transmitral gradient increased significantly during exercise (p less than 0.001), while net atrioventricular compliance decreased (p less than 0.001). MVA by the pressure half-time method increased significantly during exercise from 1.0 +/- 0.2 to 1.4 +/- 0.4 cm2 (p less than 0.001). There was no significant difference in MVA estimation using the continuity equation comparing rest to exercise, with the mean area remaining constant at 0.8 +/- 0.3 cm2 (p = 0.83). Thus, during conditions of changing hemodynamics, the continuity equation method for estimating MVA may be preferable to the pressure half-time method.