Rheumatic fever (RF) is the common cause of rheumatic heart disease (RHD) in the 5-30 age group and is usually preceded by group A streptococcal pharyngitis. The annual mortality caused by RF and RHD has changed remarkably in Japan between 1960 and 1981 according to the report of the Ministry of Health and Welfare. The annual incidence of RF among schoolchildren as surveyed from pediatric clinics of 20 major hospitals between 1952 and 1980 varied year by year, and is now steadily declining. Follow-up studies of 287 patients with carditis over ten years showed that cardiac murmur disappeared in 44.9% of total patients within 4 years through use of antibiotic prophylaxis. Other patients continued to have cardiac murmur 10 years after the first attack of RF. Valvular involvement due to RF was mostly confined to mitral valve and the appearance of mitral regurgitation was particularly common in schoolchildren. Survey of RHD in schoolchildren showed that mitral regurgitation was the most common anomaly, but the prevalence rate of RHD decreased from 4.6/1000 population in 1958 to 0.14/1000 population in 1981. By contrast, mitral stenosis was predominant in adults, according to the records of patients admitted in three university hospitals. Since socio-economic conditions have improved, and penicillin has been introduced to control group A streptococcus, mortality and morbidity from RF and RHD have remarkably decreased in well developed countries. These factors may have contributed predominantly to the sharp decrease in first and recurrent attack of RF in Japan.