Both international and Japanese cooperative studies have failed to prove the positive effects of EC-IC bypass surgery for the prevention of stroke. However, we believe STA-MCA anastomosis is effective in improving the symptoms of hemodynamic cerebral hypoperfusion. Our candidates of STA-MCA anastomosis are stroke patients with both reduced cerebral vascular reserve and clinical symptoms due to cerebral hypoperfusion. The anastomosis to the insular segment of MCA can offer more blood supply than the anastomosis to the cortical branch, and is less invasive than the high flow bypass. It is also indicated in aneurysm cases of the intracavernous internal carotid artery with good collateral circulation.