From 1981 to 1999 Mitral bileaflet prosthesis was implanted to 90 patients. Doppler echocardiography was performed for these patients between January and March 2002 with a mean deadline of 111 months after the intervention. 36 were women (40%) and 54 were men (60%) the mean age was 41 years (20 - 70 years) The mitral bileaflet prosthesis was a Saint Jude in 65 cases, Jyros 8 cases, Carbomédics 7 cases, Sorin Bicarbon 7 cases, Edwards Duromédics 2 cases et an ON-X in one case. The maximal transprosthetic gradient was 15.7 mm Hg +/- 5.06 (6.25 mm Hg). The mean transprosthetic gradient was 5.6 mm Hg +/- 1.07 (39.5 mmHg). The mean prosthesis functional area 2.37 cm2 +/- 0.44 (1.75 cm2 et 3.60 cm2). Maximal gradient, mean gradient and prosthesis functional area are independent from kind mitral bileaflet prosthesis and from the prosthesis size.