Using combined two-dimensional echocardiography and Doppler technique in 30 patients with pure mitral valve stenosis or combined valve disease with prevailing mitral stenosis, the mitral valve area and diastolic pressure gradient were determined, and compared to the invasively recorded values obtained during heart catheterization. Four patients were examined by Doppler ultrasound before and after mitral valve replacement. The determination of the mitral valve area was performed 1) invasively by means of the formula derived by Gorlin (and measured between 0.5 and 2.9 cm2), 2) by means of planimetry by integration of the two-dimensional echo in the short-axis view (between 0.7 and 2.8 cm2), and 3) by Doppler ultrasound based on the formula 220/t1/2, whereby the pressure half-time was obtained by dividing maximum flow velocity by square root 2. Here, the mitral valve area was between 0.5 and 2.8 cm2. The correlation between values obtained invasively and by means of Doppler ultrasound was good (r = 0.86), and compared well to the correlation between two-dimensional echocardiography and heart catheterization (r = 0.88). The best correlation of r = 0.89 was found between the mitral valve areas obtained by Doppler ultrasound and two-dimensional echocardiography. The diastolic pressure gradient was calculated by means of the formula derived from the Bernoulli equation, which is: delta P = 4Vmax2, whereby Vmax equals the maximum transmitral flow velocity. The invasively measured pressure gradients were between 2 and 30 mm Hg, the values obtained by Doppler ultrasound were between 6 and 29 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)