The ratio of ankle-to-arm systolic blood pressure (ankle/arm index or AAI) appears to be a non-invasive indicator of flow-significant atherosclerosis and may be a useful measure of burden of disease in a high risk population. The prevalence of lower extremity arterial disease (LEAD) was assessed by this method in the Systolic Hypertension in the Elderly Program (SHEP). Subjects were aged 60 and older with systolic blood pressure greater than 160 mmHg upon entry to the study. An AAI of 0.90 or less was considered indicative of flow-significant LEAD,. The prevalence of LEAD by this method was 26.7% ( 50 187), while the prevalence of intermittent claudication (IC) was only 6.4% ( 12 187). Of those with IC, 66.7% ( 8 12) had confirmed LEAD. The prevalence of LEAD as measured by AAI increased with age in women and was associated with a history of current smoking and lower levels of high density lipoproteins. In this study population with systolic hypertension, LEAD, as measured by the AAI, is more prevalent than previously described in elderly populations and is associated with other risk factors for atherosclerosis. © 1991.