A 13 year old girl with multiple arterial stenoses of unknown aetiology is described. At the age of seven months she was noted to have cardiomegaly and diminished left ventricular ejection fraction with no cardiac anomaly. Cardiac function gradually improved and her condition remained satisfactory until she was 11 years old when multiple lesions in the coronary, cerebral, and left brachial arteries were diagnosed. Histological examination of an endomyocardial biopsy specimen from the right ventricle showed hypertrophic muscles surrounded by abundant fibrous tissue. Percutaneous transluminal angioplasty of the right coronary stenoses led to complete occlusion.