The effect of superior cervical ganglionectomy (SCG) on cerebral blood flow and metabolism was investigated in moyamoya disease. Measurement of cerebral blood flow and metabolism was performed in 12 cases (15 operations) of moyamoya disease during SCG. Mean age was 65.2 years (from 3 to 38). 4 were male and eight were female. Ischemic cases were 8 and hemorrhagic cases were 4. At encephalo-duro-anterio-synangiosis, a Laser Doppler flow meter and probes for measuring cortical tissue oxygen and carbon dioxide were set out to allow measurement from identical sites on the surface of the brain over the cortex. Moreover, an electromagnetic flow meter was placed on the common carotid artery. And the mean arterial blood pressure was also measured from femoral artery. After the electrode had been stabilized, continuous recordings were made of cerebral blood flow and metabolism during SCG. The mean arterial blood pressure fell slightly post operatively, but the changes in blood pressure were considered not to be significant enough to affect blood flow. Cortical CBF did not change immediately after SCG. However it increased gradually to 118.8% of preoperation level 30 minutes later respectively, and the difference was observed significant. The carotid blood flow and the tissue oxygen developed a tendency to increase after 30 minutes, but the tissue carbon dioxide did not changed. The present study indicates that superior cervical ganglionectomy is the useful procedure to increase in cerebral blood flow immediately after the operation on patients with moyamoya disease.