In patients with a systolic ejection murmur and without a history of rheumatic fever, a probable diagnosis of idiopathic hypertrophic subaortic stenosis (IHSS) can be made from the roentgenologic findings. Left ventricular enlargement, associated at times with minimal left atrial enlargement, without intracardiac calcification and with a normal ascending aorta are the most frequent roentgen findings. For a positive diagnosis, a pressure gradient within the left ventricle and hypertrophic muscular obstruction should be demonstrated by angiocardiography.