Although mucolipidosis, a fatal metabolic storage disorder, is associated with cardiovascular abnormalities, detailed, non-invasive cardiac examinations have not been well documented. We studied 4 children with type II and type III mucolipidosis, 3 of whom had unequivocal evidence of aortic regurgitation characterized by phonocardiography and M-mode echocardiography. Two-dimensional echocardiography showed an aortic valve prolapse in 3, a mitral valve prolapse in 2 and a tricuspid valve prolapse in 1. The QT interval was prolonged in 2 cases. In 1 autopsy case, we found considerably thickened and retracted aortic, mitral, and tricuspid valves, and accumulation of the foam cells in the myocardium. Echocardiography revealed similar findings in another 3 cases. We conclude that cardiac manifestations in this disorder should be examined carefully particularly by the use of echocardiography which is an excellent technique for detecting cardiovascular abnormalities in mucolipidosis.