Flow-augmentation bypass aims to enhance blood flow to hypoperfused brain regions in patients with cerebrovascular steno-occlusive diseases. This surgical procedure is indicated for ischemic and hemorrhagic moyamoya vasculopathy and for selected patients with chronic steno-occlusive disease and acute ischemic stroke. Flow-augmentation bypass has been rigorously evaluated in randomized clinical trials, including the EC-IC Bypass Trial, the Carotid Occlusion Surgery Study (COSS), the Japanese Adult Moyamoya (JAM) trial, and the recent Carotid and Middle Cerebral Artery Occlusion Surgery Study (CMOSS). In this article, we examine the current indications and outline the diagnostic and therapeutic decision-making processes for patients with steno-occlusive disease who are candidates for flow-augmentation bypass surgery.