Rat fetal brain glycogen content, and glycogen synthase and phosphorylase activities were measured both in control and in hypoxia on 17th, 19th and 21st days of gestation. Glycogen distribution in the brain was also observed with an optical microscope. The results obtained were as follows: 1. Glycogen content was highest in the choroid plexus, and there tended to be located more in the periventricular areas and hemispheric surface layers of the cerebrum than in other areas. 2. Glycogen content increased from the 17th day, reaching a peak on the 19th day; it decreased with age thereafter and had decreased significantly by the 21st day. 3. Glycogen synthase a-type activity showed no change with fetal age. 4. Glycogen phosphorylase activity was lowest on the 17th day, and it increased thereafter with age. 5. When an ischemic load was applied, brain glycogen content decreased and glycogen phosphorylase a-type activity increased on the 17th and 19th days. The abovementioned findings suggest that glycogen in the rat fetal brain is distributed in the most likely sites of intracranial hemorrhage. The amount of glycogen in the rat fetal brain may depend on glycogen phosphorylase activities. Glycogen may be used as an energy source to maintain brain tissue function during hypoxia. It is also possible that glycogen plays a role in brain maturation.