OBJECTIVE Aortic knob calcification (AC) is associated with increased risks of cardiovascular and cerebrovascular events. We evaluated the clinical importance of AC in ischemic stroke patients with intracranial (IC) stenosis using simple, non-invasive and routine chest radiography. METHODS The presence of AC was assessed in a chest posteroanterior view in 307 acute ischemic stroke patients admitted from May 2009 to April 2010, and who underwent magnetic resonance angiography or distal subtraction angiography. The association of AC with IC stenosis was analyzed. RESULTS Patient age (68.3±8.7 vs. 65.9±8.27 years, P=0.04), and the prevalence of IC stenosis (70.7 vs. 41.3%, P<0.01) were higher in patients with AC than in patients without calcification. After adjusting for age, gender and vascular risk factors, logistic regression analysis showed that AC (Odds ratio, 3.54; 95% confidence interval, 1.90 to 6.61, P<0.01) and age (Odds ratio, 1.79; 95% confidence interval, 1.01 to 3.19; P=0.04) were independent factors affecting IC stenosis. CONCLUSIONS AC appears to be a reliable predictor for IC stenosis, an important mechanism of ischemic stroke.