Infective endocarditis is a rare disease in the general pediatric population. Nonetheless, children with congenital heart disease have a substantial lifetime risk for development of endocarditis, and recent advances in the management of these children should increase the number of patients who survive infancy and early childhood. During the 30-year period from 1950 through 1979, 50 cases of endocarditis in children were diagnosed at the Mayo Clinic. Of these 50 patients, 37 had congenital heart disease, and 8 were diagnosed as having endocarditis within 3 months after having undergone a cardiac surgical procedure. Nineteen patients died of the disease or its complications. The most common organism isolated at Staphylococcus aureus (19 patients), followed by viridans streptococci (14 patients). Children younger than 10 years of age experienced a particularly high mortality, as did patients of all ages with S. aureus infection. Any unexplained fever in a child with congenital heart disease deserves close investigation; if endocarditis is suspected, early empiric antibiotic therapy is indicated after appropriate culture specimens have been obtained. Moreover, localized bacterial infections in children at risk must be treated aggressively to prevent metastatic spread to the heart.