Marfan syndrome is a hereditary disorder of connective tissue fibers, involving skeleton, eye and cardiovascular system. The cardiovascular complications, directly related to the cause of death, are associated with about 90% of the Marfan syndrome. The cardiovascular complications are aortic and mitral insufficiency, mitral valvular prolapse, bacterial endocarditis, arrhythmia and aneurysm of interatrial septum and aorta. Among the cardiovascular complications, bacterial endocarditis is unusual. The aortic valve, though commonly abonormal in Marfan syndrome, was rarely involved by endocarditis. In contrast the mitral valve was the favoured site of infection in these patients. The low incidence of aortic valve involvement remains unexplained. There is extreme mortality in Marfan patients affected by endocarditis. A 22-year-old man was admitted to Wallace Memorial Baptist Hospital because of intermittent fever with chill, dyspnea and orthopnea. He had characteristic Marfanoid features such as a slender body with sparsity of subcutaneous fat, arachnodactly and disproprtionate long extremities, axial myopia as well as suspicious family history. Three blood cultures produced a slowly growing γ-hemolytic streptococcus sensitive to penicillin. Chest X-ray revealed increased C-T ratio and generalized congested lung parenchyme and increased lung markings with multiple dense, horizontal lines, so called Kerley's B lines. Echocardiogram showed thickened bicuspid arotic valve with vegetation and enlarged left ventricular cavity, grade 3/4 mitral and aortic regurgitation. The authors have experienced a rare case of Marfan syndrome with subacute infective endocarditis.