Current neuropsychological research supports a model postulating that prefrontal functions are among the first to decline in normal aging, but this model has rarely been empirically tested with subjects of 65 years or less. This study tests the following hypotheses: (a) A significant decline occurs prior to age 65 in a wide ranging set of prefrontal performance measures and (b) a significant increase occurs on measures of perseveration based on the same prefrontal tasks. A group of young adults (n = 70) aged 20 to 35 and a group of elderly adults (n = 58) aged 45 to 65, group‐matched for education and sex, were evaluated by means of six neuropsychological prefrontal tasks: the Self‐Ordered Pointing Task, the Wisconsin Card Sorting Test, the Porteus Mazes, a Verbal Fluency Task, a Design Fluency Task, and the Stroop Test. Four of the six prefrontal scores and four of six measures of perseveration manifested significant declines in the elderly group, suggesting that normal aging prior to age 65 may exhibit measurable deterioration of prefrontal brain function: decreased ability to regulate behavior on the basis of plans, abstract concepts, environmental feedback, or one's own responses.