The cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) were measured in 17 children with “Moyamoya” disease (mean age of 8.6±3.4 years), by the argon method and medical mass spectrometry. Sequential changes of CBF and CMRO2 were monitored before surgery and the second day, 1st month, 3rd month and 6th month after surgery. Seventeen children were divided into three groups according to the neurological symptoms : groups with a transient ischemic attack (TIA), with a minor stroke, and with a major stroke, respectively. Before surgery the CBF in the TIA, minor stroke, and major stroke groups were 40.0, 38.2, and 39.6 ml/100 g/ min., respectively. The CMRO2 in the TIA, minor stroke, and major stroke groups were 2.73, 2.21, and 1.86 ml/ 100 g/min., respectively. The CBF and CMRO2 decreased with advancing age. The mean ages of the cases with a TIA, minorstroke, and majorstroke were 9.5±4.0, 10.3±2.4, and 5.4±2.2 years, respectively. From these results, the CBF and CMRO2 in the major stroke group seemed to definitely decrease when compared with the other groups. The cerebrovascular resistance (CVR) in groups of TIA, minor stroke, and major stroke were 2.21, 2.43, and 2.80 mmHg/ml/100 g/min., respectively. ST-MC anastomoses were performed in 12 hemispheres and encephalo-myo-synangiosis in 10 cerebral hemispheres. The CBF after these neurosurgical procedures increased on the 2nd day, and then decreased until the end of the 1st month. The CBF gradually increased thereafter. The CBF 6 months after surgery significantly increased when compared with that before surgery. The CMRO2 6 months after surgery also increased, when compared with that before surgery. The CVR 6 months after surgery decreased, when compared with that before surgery. In the patients who had transient ischemic neurological symptoms at their acute stages after surgery, a marked reduction of CMRO2 was characteristic, in spite of the increase in CBF. This uncoupling phenomenon between CBF and CMRO2 might be ascribed to the brain edema following disruption of the blood brain barrier due to surgery. From this evidence the main feature of pathophysiology of cerebral circulation and metabolism in cases of “Moyamoya” disease was a marked hypoperfusion and reduction of oxygen consumption of the brain. After neurosurgical interventions the cerebral blood flow and the cerebral oxygen consumption gradually increased and this was compatible with the clinical improvement.