We analyzed the results obtained in 163 consecutive patients with "pure" mitral stenosis who underwent operation by the open approach exclusively. Calcification was found in the mitral valve leaflets in 11% of the patients and left atrial thrombus, in 13.2%. A statistically significant relationship was discovered between history of previous systemic embolism and cardiac rhythm (p less than 0.005). The subvalvular apparatus was affected in 66.6% of patients; most of them were in New York Heart Association Functional Class III (p less than 0.005). The frequency with which annuloplasty had to be performed because of mitral insufficiency after commissurotomy was statistically higher (p less than 0.025) among patients in Functional Class III. Early mortality was 1.2% and late mortality, 0.2% per patient-year. Two patients required late reoperation (0.4% per patient-year). One was in Functional Class III and the other, Functional Class IV before the first operation. Three patients sustained a late systemic embolism (0.6% per patient-year). All survivors but 1 are in Functional Class I (84.4%) or II (14.9%).