The amount and distribution of glycogen in the brain tissue in closed craniocerebral injury were studied by electron microscopy. It is shown that 24 hours after the injury the number of glycogen granules in different areas of the brain, and especially in its stem, increases sharply. The glycogen granules are found in the cytoplasm of the neurones and their processes, in the synapses, and in the cytoplasm of the glial cells. The amount of glycogen reduced when the animals were given injections of agents stimulating the central nervous system (phenamine). In contrast, inhibition of the function of the central nervous system by injection of urethane and barbital caused an increase in the glycogen content. Under such conditions, the glycogen particles were predominantly localized in the processes of the perivascular astrocytes. The change in the glycogen content is associated with the effect of the craniocerebral injury and the different functions of the central nervous system on the activity of the enzyme gamma-amylase which is concerned with the hydrolysis of glycogen and the ultimate formation of glucose, the most important energy substrate of the brain.