A recent interest in aging of the nervous system is related to the remarkable increase in the numbers of elderly persons throughout the world. As a reflection of the added years, pathologies in the older person have also increased. Primary among those which affect the activities and behavior of these people are the dementias, especially Alzheimer's Disease. To focus on such problems, however, requires an understanding of the changes which take place in the normal aging nervous system. This paper reviews some of the accepted criteria for these changes as well as the possible attempts by the nervous system to alter its structure in response to these changes.