Oculocraniosomatic neuromuscular disease (ragged red fibers) has been associated with mitral valve prolapse and other cardiac abnormalities. Using echocardiography, 24 hour ambulatory ECG monitoring, and routine ECG, cardiac abnormality was noted in 7 (64%) of 11 patients studied. These included left anterior hemiblock, bifascicular block, supraventricular arrhythmia, and high grade ventricular ectopy. Mitral valve prolapse on echo was present in only 2/11 patients - neither of who had supporting auscultatory findings. Cardiac chamber dimensions and resting left ventricular function, determined by echocardiogram, were normal in all patients.