This study describes the clinical, anatomic, echocardiographic, and Doppler features of 13 patients with mitral valve aneurysms. Eleven patients had definitive criteria for infective endocarditis. Transesophageal echocardiography was superior to conventional echocardiography in detecting and assessing aneurysms. Patients with heart failure required surgery. Echocardiographic detection of this lesion should not be, by itself, an immediate surgical indication.