The normal hemodynamic parameters of 90 patients with St. Jude bileaflet valve, Medtronic-Hall, Sorin and GK tilting disc valves were investigated and compared to those of 30 control subjects by transthoracic Doppler echocardiographic technique. The results showed that although the mitral prosthetic valve area increased significantly and the peak velocity and the peak pressure gradient decreased significantly after mitral valve replacement, the effective orifice area (EOA), peak velocity (Vmax), and peak gradient (PG) in 4 different prosthetic valve groups still had significant differences from those of the normal native valve group. Among the 4 types of prosthetic valves St. Jude bileaflet valve had the largest EOA (3.12 +/- 0.47 cm2) and the lowest peak pressure gradients (9.3 +/- 1.1 mmHg). The EOA of the other 3 types of tilting disc valves showed no significant difference. The possibility of determining the indication of mitral valve replacement by Doppler echocardiography was also discussed.