Placebo and ACTH 4-10 (in ascending dosages from 15 to 60 mg) were administered subcutaneously to normal aging subjects (mean, 65.6 years). Measurements were obtained for EEG, EKG, SMA-12, urine, and blood pressure. Behavioral tasks measuring reaction time (RT), short-term memory, perceptual speed, and motor speed were administered. There were no pre- to post-injection changes in SMA-12, urine, EEG, and EKG. There was an improvement in RT time that was dose related. These data indicate that ACTH 4-10 is (1) safe to administer to an aging population and (2) combined with data on young adults suggest that it may act on the attentional/arousal processes. Results suggest that ACTH 4-10 may have stimulant-like properties on behavior without effecting the CNS and cardiovascular system.