Background: Intracranial arterial stenosis (ICAS) is the dominant cause for ischemic stroke worldwide, with hemodynamic compromise as a crucial contributor. Prolonged perfusion is commonly observed in ICAS patients on CT perfusion (CTP) maps, while the clinical significance of this perfusion pattern has not been elucidated.Method: Patients having symptomatic ICAS of 50-99% stenosis with sustained downstream cerebral blood flow (CBF) were enrolled in this study. Prolonged perfusion was defined as increased mean transit time (MTT) in vascular territories of the target ICAS on CTP maps. The primary clinical outcome was recurrence of ipsilateral ischemic stroke, and secondary outcome was any ipsilateral ischemic events at 2 years follow-up. Results: Of the 95 patients (median age 61y; 70% males) with symptomatic ICAS, 29 patients (30.5%) had prolonged perfusion. Such delayed perfusion was persistent in a majority of patients according to the 1-year imaging follow-up. The prolongation of cerebral perfusion was associated with subsequent risk for ipsilateral ischemic stroke (HR 7.01; 95% CI 1.86-26.46; p = 0.004), but not for any ipsilateral ischemic events (HR 1.52; 95% CI 0.63-3.68; p = 0.348). Further comparison of perfusion measures showed lower CBF (p = 0.034) and higher MTT (p = 0.064) in patients with recurrent ischemic stroke, but not in those with recurrent transient ischemic attack (TIA). Among patients with recurrent stroke, a majority had multiple infarcts along the borderzone regions. Conclusion: In patients with symptomatic ICAS, persistent prolonged cerebral perfusion might contribute to the relapse of ischemic stroke, but not TIA.