The follow up study on rheumatic heart disease was carried out over a 20 year period by the questionaire method. Two hundreds and seventy-nine patients were analyzed and the following results were obtained. 1) Sixteen cases (5.5%) died, 20 cases (6.8%) showed deterioration, 155 cases (53.1%) were unchanged, 35 cases (12.0%) were improved, 12 cases (4.1%) were announced that their valvular lesions disappeared and 22 cases (7.2%) underwent cardiac surgery. The more severe the findings at the final examination under our program, the poorer the courses. 2) The cases having a severe status index showed a tendency for poor prognoses. Mitral steno-regurgitation revealed the poorest prognoses. 3) 84.3 per cent of the living cases were found to be leading normal daily lives without any restriction. 4) The average death rate was 1.0% per year during the 20 years between 1958 and 1978. The death rate for age group between 9 and 17 years old was the highest (1.34% per year). 5) The leading cause of death in every group including all the cases under our program was a recurrence of rheumatic fever. However in groups older than 18 years of age chronic congestive heart failure and unsuccessful cardiac surgery were leading causes.