Between Oct. 1985 and July 1995, 230 patients underwent mitral valve replacement. There were 77 men and 153 women whose mean age was 35.7 years, range 9 to 62 The concomitant operations were 40 aortic valve replacements(17.4%), 25 tricuspid annuloplasties(10.4%), 8 aortic valve replacements & tricuspid annuloplasties(3.5%), 2 tricuspid valve replacements(0.9%) and others, We used 139 mechanical (76 51. Jude medical, 33 CarboMedics, 30 Sorin) and 91 tissue 386 Carpentier-Edwards, 5 lonescu-Shiley) valves. The early postoperative complications occurred in 28 cases. There were 8 low cardiac output syndrome, 5 pleural effusion, 3 significant arrhythmia, 2 cardiac rupture and others. There were 6 early hospital deaths (2.6%) due to low cardiac output syndrome(2), arrhythmia(2) and ventricul r rupture(2). The cuAmulative notal follow-up period was 764. 4 patient-years with a mean of 4).9 months. The long term follow-up information was available for 212 patients(94.6%). There were 21 cases of valve-related complications. Prosthetic valve failure(10), anti-coagulation related bleeding (5), prosthetic valve endocarditis (4), and thromboembolism (2) occurred at rates of 1.3, 0.7, 0.5, and 0.3%Ipt-yr respectively. Late death occurred In 5 cases (0.7%/pt-yr) associated with prosthetic valve endocarditis (2), heart failure (2) and anti-coagulation related bleeding (1). There was no difference in the rate of freedom from prosthetic valve failure between the mechanical and tissue valve group at 6 years (100%), but there was significant difference at 9 years between the tissue (34.4%) and mechanical valve (100%) group (p=0.032). Actuarial survival rates were 98. 8% in tissue valve. 9).7% in mechanical valve group and 96.6% in total patients at 9 years.