Computed tomographic (CT) studies during life reveal the involutionary changes in the brain found in postmortem studies. Beginning about the fourth decade, gradual widening of the third ventricle, sylvian and interhemispheric fissures, superficial sulci, and basal cisterns occurs. Enlargement of the lateral ventricles is most striking after the sixth decade of life. Regression of the brain with aging is a normal process. There is marked individual variation in the degree of involutional changes; not all lives are identical, and the longer the life span the less predictable one would expect the involutionary changes to be.