Objective To investigate the correlation between vertebral artery dominance (VAD) and posterior circulation ischemic stroke (PCIS).Methods The consecutive patients with acute ischemic stroke hospitalized from November 2013 to October 2015 were collected.All patients underwent MRI and magnetic resonance angiography (MRA).The dominant vertebral artery was defined as having the larger diameter if left and right diameter difference ≥0.3 mm or the vertebral artery connected to the basilar artery in a more straight fashion if the diameter difference ＜ 0.3 mm.They were divided into either an anterior circulation ischemia stroke (ACIS) group or a PCIS group according to the classification criteria of Oxfordshire Community Stroke Project (OCSP).A multivariate logistic regression analysis was performed to investigate the correlation between VAD and PCIS.Results A total of 226 patients withacute ischemic stroke were enrolled,including 172 patients (76.1％) in the ACIS group and 54 (23.9％) in the PCIS group.Fifty-four patients (23.9％) had VAD,including 38 (70.3％) on the left and 16 (29.7％) on the right.The proportion of the patients with VAD in the PCIS group was significantly higher than that in the ACIS group (55.6％ vs.14.0％;x2 =39.115,P ＜ 0.001).Multivariate logistic regression analysis showed that VAD was an independent risk factor for patients occurring PCIS (odds ratio,13.60,95％ confidence interval 6.90-27.01;P＜0.001).Conclusions VAD is closely associated with the occurrence of PCIS,and it is an independent risk factor for PCIS.