Hypertrophic cardiomyopathy (HCM) is infrequently complicated by infective endocarditis (IE). The authors report the case of a 46-year-old woman developing IE in asymptomatic HCM. Blood cultures were positive for Streptococcus viridans. Echocardiography demonstrated: 1) a mobile (1.2 x 1 cm2) vegetation attached to the septal endocardium at the site of contact between the mitral valve leaflet and the hypertrophic septum; 2) two large (2.7 x 1.7 cm2 and 1.6 x 1.1 cm2) vegetations at NCC and RCC respectively of aortic valve, causing moderate valve regurgitation, and, 3) a mural (1 x 0.8 cm2) vegetation on the posterior wall of the left ventricle. On the third day of hospitalization, the patient underwent aortic valve replacement and removal of the vegetations. Antibiotics were continued for another four weeks. The patient recovered and follow-up was uneventful. Thus, chronic endocardial trauma of the septum, a common finding in HCM with outflow tract obstruction, may provide a fertile nidus for the development of vegetation, which in turn would play the major role in the pathogenesis of IE.