Total 145 cases mitral vlave replacement were performed in Department of Thoracic and Cardiovascular Surgery in Chungnam National University Hospital during the period from May 1983 to July 1991. Sixty-one patients were male and 84 patients were female and the range of age was from 12 to 66 years old with the mean of 37.9[$pm$11.6] years. Valvular lesions were 49 cases of mitral stenosis, 18 cases of regurgitation and 78 cases of combined lesion. Used valve were Ionescu-Shiley[42 cases], Bjork-Shiley[49 cases], Inact[6 cases], St. Jude Medical[11 cases] and CarboMedics[37 cases]. Mean size of valve was 29.8$pm$1.68mm. Early morality was 13.8%[20 cases] and low output syndrome was most common cause[9 cases]. Age, functional classification and biventricular hypertrophy were risk factors. All survived cases were followed up without missing. Mean follow up period were 3 years and 3 months. Total 14 cases of death[9.7%] were observed and heart failure, unexplained sudden death and bleeding were the causes in that order. Common late complications were heart failure and bleeding related with anticoagulation. Actuarial survival rate at 5 years was 83$pm$5.4% in overall, 78$pm$7.2% in tissue valve group, 87$pm$6.8% in mechanical valve group. The actuarial freedom rate from thromboembolism at 7 years was 89$pm$8.3% in overall, 86$pm$9.9% in tissue valve group and 97$pm$1.9% in mechanical valve group. Actuarial freedom rate from bleeding at 5 years with anticoagulation was 88.9$pm$4.2% in overall, 96$pm$3.9% in tissue valve group, 86$pm$4.6% in mechanical valve group. Reoperation was done in 3 cases with heart failure with tricuspid regurgitation and thromboembolism in 2 cases. The functional status of survived cases was I or II.