Aggregatibacter aphrophilus is a facultatively anaerobic gram-negative coccobacillus or bacillus that grows with no dependence on X factor and variable requirement for V factor. The organism is normal flora in the human oral cavity and upper respiratory tract and, rarely, causes invasive infections such as bacteremia, endocarditis, brain abscess, or osteomyelitis. We report a case of septic peripheral embolism in left leg from A. aphrophilus endocarditis. A 49-year-old man with known hypertension presented with acute muscle pain in the left leg. On physical examination, a regular heartbeat with a pansystolic murmur was heard. There were decreased pulses in the left popliteal and dorsalis pedis arteries and coldness of the left foot, although sensory and motor functions were intact. Angiography revealed an embolus in a branch of the left femoral artery. He underwent emergency embolectomy, and gram-negative bacilli grew in the embolus cultures. The same microorganism was isolated in two pairs of blood culturs and subsequently identified as A. aphrophilus. Transthoracic echocardiography revealed mitral regurgitation and multiple vegetations on the mitral valve. The patient was treated with a third-generation cephalosporin for 4 weeks and mitral valve replacement in view of the diagnosis of infective endocarditis and septic peripheral embolism. (Korean J Clin Microbiol 2009;12:82-86)