BACKGROUND: The ankle brachial index (ABI) is a useful screening tool for peripheral arterial disease. It has been documented that the cerebral atherosclerosis is more frequent in stroke patients with abnormal ABI than in those with normal ABI. The present study compared the different calculation methods of ABI for coexistent intracranial and extracranial arterial stenosis (IECAS) in ischemic stroke. METHODS: We reviewed the data of patients admitted for acute ischemic stroke or transient ischemic attack. The following four distinct ABIs were calculated: the ratio of the higher (ABI-H), lower (ABI-L), or either of the systolic blood pressures (SBPs) of the posterior tibial (ABI-PT) and dorsalis pedis (ABI-DP) arteries relative to the higher of the brachial SBP. We compared the values of these four ABI measures relative to the presence of any IECAS using receiver operating characteristic (ROC) curve analysis. RESULTS: ABI-H, ABI-L, ABI-PT, and ABI-DP were abnormal (≤ 0.9) in 19 (13.1%), 36 (24.8%), 29 (20%), and 30 (20.7%) of 145 patients, respectively. The area under the ROC curve was significantly larger for ABI-H, ABI-L, and ABI-DP than for ABI-PT for any type of IECAS. The extracranial stenosis was more frequent when any of the four ABIs was abnormal, while intracranial stenosis was not correlated with the four ABIs. The IECAS was more frequent for abnormal ABI-H and ABI-DP than for normal ABIs. CONCLUSIONS: Our studies suggested that ABIs based on a higher SBP of the PT or DP (i.e., ABI-H) are more strongly associated with the presence of IECAS than are those using the SBP of the PT (ABI-PT). Extracranial artery stenosis seems to be more strongly associated with ABI than is intracranial stenosis.