One hundred fifty patients with idiopathic hypertrophic subaortic stenosis (IHSS) were followed-up for an average of 5.5 years. There were 95 males and 55 females with a mean age of 51 years. Patients usually presented with cardiac symptoms or syncope; no patient presented with stroke. Eight patients (5%) died during follow-up, all from cardiac causes. Eleven patients (7%) developed cerebrovascular complications; 5 (3%) had a stroke and 6 (4%) had TIA only. Patients with IHSS and atrial fibrillation have a much greater stroke risk. Mitral annulus calcification may also increase stroke risk in IHSS. However, stroke is almost never the presenting manifestation of IHSS, and the longterm risk of stroke for most patients with known IHSS is low.