Sixty-three patients who underwent open mitral commissurotomy at Sejong General Hospital during last 10 years from the August, 1983 to June, 1993 were reviewed There were fifty-one women and twelve men, and the mean age was 34.2 years. According to the NYHA classification, the distribution of patient preoperatively was as follows: class I, 5 patients ; class II, 26 patients ; class III, 30 patients ; class IV, 2 patients, and mean duration of symptome was 4.5 years. The mean mitral valvular area measured with echocardiogram preoperatively was 0.92cm2. All patients underwent open mitral commissurotomy and 41 patients required additional procedures for relief of subvalvular stenosis or other valvular disease. There were no operative death. 63 patients had three different types of mitral stenosis : type I, mobile cusps without subvalvular change [21 patients] ; typeII, thickened cusps with subvalvular change [34 patients] ; type III, rigid cusps with severe subvalvular change [8 patients]. The valvular calcification was seen in 11 patients [17%] and 15 patients [24%] had left atrial thrombus. The duration of follow-up was from 1 month to 168 months [mean, 39.6 months] and there were no late death. Six patients required reoperation and one patient had embolic episode. Conclusively,the open mitral commissurotomy represents a safe surgical precedure for treating mitral stenosis, allowing a complete removal of atrial thrombosis if present, and even when associated with subvalvular changes.