A community survey was conducted to determine the prevalence of rheumatic heart disease in Kenyan children in all primary schools in 2 sublocations in Western Kenya. In total, 3631 children (97% school attendance) aged from 5 to 15 years were examined by one experienced physician and 2 cardiologists between September and December 1985. Six children were found to have evidence of rheumatic heart disease, giving a prevalence rate of 1.7/1000. As all cases occurred in the age group between 10 and 15 years, the rate was calculated for this group as 2.4/1000. None of these patients had previously been diagnosed as having rheumatic fever. There were 3 males and 3 females. Four patients had mitral regurgitation, one had aortic regurgitation and one had mitral stenosis. Three had electrocardiographic evidence of left atrial abnormality and one showed findings of left ventricular hypertrophy but two patients had normal tracings. Half were symptomatic with dyspnoea on exertion and two gave a history of fleeting polyarthritis. The socio-economic status (peasant), family size (mean = 6 siblings) and the number of children sleeping per room were the same in both the cases with rheumatic heart disease and their controls. The health workers achieved low scores (mean 26%) with regard to the clinical diagnosis, treatment and prevention of rheumatic fever at the level of primary health care. Rheumatic heart disease, nonetheless, was relatively insignificant in the overall picture of health care of school children in Western Kenya.