It is considered controversial whether superficial temporal artery (STA)-middle cerebral artery (MCA) bypass affects the outcome of patients with ischemic stroke. This prospective study was undertaken to demonstrate the effect of STA-MCA bypass on the cerebral blood flow and neurological status of the patients with ischemic stroke. Seventy-five patients underwent unilateral or bilateral STA-MCA bypass surgery. The selection of the patients closely adhered to the criteria of the Japan EC-IC Bypass Trial (JET). Cerebral blood flow (CBF) before and after Diamox administration was measured by single photon emission computed tomography (SPECT) using iodine-123-N-isopropyl-p-iodoamphetamine (IMP). MRI, contrast-enhanced 3D CT scans, and angiography were performed on each patient pre- and postoperatively. Bypass surgery was successfully done in all patients. CBF was significantly increased after STA-MCA bypass (P < 0.05). In addition, reservation of CBF was significantly improved after STA-MCA bypass (P < 0.05). Patients with transient ischemic attack (TIA) did not experience recurrence of such episodes after STA-MCA bypass. The neurological deficit was unchanged in patients with complete stroke after bypass surgery. However, the NIH stroke scale was significantly improved after bypass surgery (P < 0.01). In addition, the satisfaction rate of treatment as assessed by the patients themselves was very high after STA-MCA bypass (>90%) compared to the conservative treatment group (<50%). STA-MCA bypass still plays a limited role in the treatment of ischemic stroke, but may become a bright hope in depressed patients after cerebral ischemia.