Although gonococcal infections of the pulmonary valve were common before the introduction of antibiotics, such infections have rarely been reported since penicillin became available. In an elderly man with gonococcal endocarditis of the pulmonary valve the non-specific signs and symptoms, the late appearance of a pulmonary murmur, and the sterility of early blood cultures made the diagnosis unclear until three weeks after admission. Endocarditis was localised to the pulmonary valve by M-mode and cross-sectional echocardiography. Echocardiography may be useful for diagnosing endocarditis in patients with fever of unknown origin. Gonococcal infection should be suspected in patients with pulmonary vegetations and sterile blood cultures.