The epidemiology of rheumatic fever and rheumatic heart disease in a rural community (total population 114,610) in northern India was studied by setting up a registry based on primary health care centres. Health workers and schoolteachers were trained to identify suspected patients in school and village surveys (121 villages). Medical specialists screened 5-15-year-olds (n = 31,200). The population was followed up for 3 years (from March 1988 to March 1991). All suspected and registered cases were investigated by serial echocardiography and Doppler ultrasonography at a tertiary care centre. A total of 102 cases were confirmed to have rheumatic fever/rheumatic heart disease (prevalence, 0.09%); 66 were aged 5-15 years (prevalence, 0.21%). A total of 48 patients (24 males, 24 females; mean age, 12.11 +/- 3.7 years) were diagnosed to have a possible first attack of rheumatic fever (incidence, 0.54 per 1000 per year). Arthritis was observed in 36 (75%) and carditis in 18 (37.5%) of cases. Prolapse of the anterior mitral leaflet into the left atrium occurred in 5 (22%) cases with carditis. Mitral regurgitation was observed in all 18 cases of carditis; over the period of observation it disappeared in three cases and progressed to mitral stenosis in a further three. A total of 22 patients (11 males, 11 females; mean age, 19.41 +/- 8.1 years) were registered as rheumatic fever recurrences, and 32 patients (18 females, 14 males; mean age, 22.1 +/- 10.1 years) had chronic rheumatic heart disease. Of those with recurrences, 9 (41%) had carditis and 11 (50%) had arthritis.(ABSTRACT TRUNCATED AT 250 WORDS)