Hypoxic encephalopathy during the late gestation and perinatal period occupies a large part as a cause of mentally and physically handicaps. An extensive study on the pathogenesis and pathophysiology of the hypoxic brain damage is, therefore, the matter of urgency to minimize the occurrence of handicapped children. The main factors and/or processes relating to hypoxic or hypoxic-ischemic brain damage are (1) structural and functional immaturity of the brain vascular system and (2) a metabolic cascade triggered by hypoxia. As the following metabolic cascade subsequent to hypoxia has been partly made clear; (a) disturbance of the energy metabolism, (b) excessive release of excitatory amino acids and subsequent activation of NMDA and K/Q receptors at the cell membrane, (c) collapse of the membrane ion pump, and (d) increase in turnover of membrane phospholipids.