A 4-year-old girl presented with clinical evidence of infective endoca
rditis involving her aortic valve, but blood cultures were sterile. Se
rologic studies and analysis of resected valve by immunohistochemistry
and polymerase chain reaction established the diagnosis of Bartonella
henselae endocarditis. Clinicians should be aware that B. henselae ca
n cause apparent culture-negative endocarditis in children.