Background: Until mid-2010, intravenous thrombolysis remains the only reperfusion therapy for acute ischemic stroke. In 2015, the five pivotal endovascular recanalization therapy (ERT) trials demonstrated that ERT improved the prognosis of acute ischemic stroke with large artery occlusion within 6 hours after onset. Currently, ERT has been established as a crucial acute ischemic stroke treatment option. The prognosis of acute ischemic stroke is known to be time-dependent. Several studies addressed that ERT expands the time window for reperfusion therapy; thereby, improving prognosis.Current Concepts: Recent randomized clinical trials revealed that ERT improved the outcome in patients even within the late time window of up to 24 hours of stroke onset. The trials enrolled participants who had target mismatch, defined as either clinical-core or perfusion-core mismatch, which prompted an update of the national guidelines in several countries. To select the patients with stroke who were eligible for ERT, advanced imaging tools could be recommended.Discussion and Conclusion: According to the updated ERT guidelines, stroke centers were recommended to establish an appropriate imaging protocol and strategy for patients with acute ischemic stroke who were within the late time window. Additionally, if ERT is further practiced nationally, more manpower and infrastructure for patients with stroke should be supported at the stroke center.