From January 1981 through February 1985, 241 patients with rheumatic mitral valve disease (mean age 21.5 +/- 11.8 years) were subjected to comprehensive mitral valvuloplasty. One hundred seven patients (44.4%) were 15 years or younger and 63 (26.1%) were 12 years or younger. One hundred seventy five patients had pure or predominant regurgitation (mean age 19.3 +/- 10.7 years) and 40 (16.6%) had active rheumatic carditis at the time of the operation. Almost all patients (229) were in New York Heart Association Functional Class III or IV. The techniques used included shortening of anterior leaflet chordae tendineae (136 patients), resection of secondary, tertiary, and basal posterior leaflet chordae (156 patients), commissurotomy (113 patients), and implantation of a Carpentier ring (164 patients). Current operative mortality is 1.9%. The survivors were followed up for 576 patient-years (mean 2.64 +/- 1.32 years). Late mortality was 2.60% per patient-year and was valve related in 1.04% per patient-year. Reoperation was required in 25 patients (4.34% per patient-year), mostly (72%) in the first year. There were only two cases (0.35% per patient-year) of thromboembolism and three cases (0.52% per patient-year) of infective endocarditis. Hence valve failure occurred at a linearized rate of 6.08% per patient-year but was fatal in only 22% of the patients. There was no relationship between valve failure and the type of lesion or procedure performed, but reoperation was required more frequently in patients aged 12 years or less (7.33% per patient-year) than in those older than 12 years (3.29% per patient-year) (p less than 0.05). Actuarial survival rate at 41/2 years was 90%, and 82% of the patients were free from valve-related complications. Valve function after valvuloplasty was assessed clinically. Eighty-four percent of the patients had a good immediate result, but this figure dropped to 69% at the end of the follow-up period (p less than 0.05). The remainder had moderate valve dysfunction. However, 85% of the patients remain in New York Heart Association Functional Class I. Mitral valvuloplasty is an excellent alternative to valve replacement in young patients with rheumatic mitral valve disease. Persistent or reactivated rheumatic carditis may be a significant factor of valve failure, and penicillin prophylaxis is mandatory after operation.