We examined 11 children with infective endocarditis initially and serially by two-dimensional echocardiography. Nine (82%) of the 11 patients had echocardiographic findings at initial examination compatible with infective endocarditis. These results provided strong evidence in support of the diagnosis before bacteriologic confirmation was available. Congestive heart failure, major emboli, and/or the need for surgical intervention occurred in seven of the nine patients with positive two-dimensional echocardiograms. Echocardiographic evidence of vegetations persisted during antibiotic therapy and resolved slowly during many months. Serial echocardiograms were useful in cases in which obvious valve destruction or marked increase in vegetation size imaged echocardiographically could be combined with clinical evidence of progressive heart failure to support a decision for early surgical intervention. Two-dimensional echocardiography can make important contributions to the diagnosis and management of children with infective endocarditis.