This study was conducted to determine the prevalence of rheumatic heart disease (RHD) and congenital heart disease (CHD) in primary schoolchildren of Menoufia, Egypt and to study the relationship between these two problems and socioeconomic conditions. A total of 8000 children were screened for cardiac disease in their schools. Children with confirmed RHD and CHD in addition to 200 healthy children (controls) were visited at their homes to assess their social environment and other factors according to a designed questionnaire. We found prevalence rates of 3.4/1000 and 2.6/1000 for the RHD and CHD respectively. The most common cardiac defects were double mitral and pulmonary stenosis in the RHD and CHD groups respectively. Nineteen (39.6%) of the patients were diagnosed for the first time during the study. Penicillin prophylaxis was received by only four (14.8%) of the RHD children and none of the CHD children. The number of other affected siblings, increased multiparity, repeated abortion, and intake of contraceptives by mothers were significantly higher in families of the children with CHD. The proportion of illiterate, unskilled, and heavy smoking fathers was higher in the two patient groups. Family income was lowest in the RHD group, while increased crowding index and low whole social environment were significantly related to both RHD and CHD. Effective programs at the community and health service levels are needed in Menoufia to solve the problem of heart disease in schoolchildren in the immediate future.