A study is reported of an annual follow-up over a 15to 20-year period of the survivors of the first 1,000 patients undergoing closed mitral valvuloplasty for mitral stenosis. In addition to a report of the status of the patients at each year of follow-up, a detailed analysis has been made of the factors influencing results of surgery 15 years after operation. The most important factor adversely influencing long-term results is significant mitral valve calcification. This is true regardless of age, sex, preoperative status, concomitant mitral insufficiency or minor degrees of aortic valve disease. A beneficial effect of younger age (below 40 years at surgery) or lack of associated mitral insufficiency is apparent only in Group III patients with noncalcific valves, and in these two subgroups the results were 41 and 37 percent improved, respectively. These figures do not include the large number of patients who have again been improved following a second or even third operation. Late systemic embolization occurs infrequently after such surgery. (1.1% per patient year of follow-up). In patients without significant valvular calcification and without substantial mitral incompetence or significant associated valvular disease, closed mitral valvuloplasty is the operation of choice. The indications for closed versus open operation for mitral stenosis are discussed in detail. 17. MULLN EM JR, GLANCY DL, HIGG LM, EPSTEIN SE, MoRRow AG: Current results of operation for mitral stenosis: clinical and hemodynamic assessments in 124 consecutive patients treated by closed mitral commissurotomy, open commissurotomy or valve replacement.