The immediate response of stress to aerobic exercise was measured by utilizing the Palmar Sweat Index (PSI) and the State-Trait Anxiety Inventory (STAI). Forty subjects (20 male and 20 female) from the ages of 18-30 sustained a single bout of aerobic activity for 30 minutes at 60 percent of their maximum heart rate. Pre-treatment procedures included administration of the STAI and obtaining a finger print for determining enumeration of open sweat pores. Each subject's resting heart rate was then determined so that the treadmill could be adjusted until the target heart rate was reached. After the half-hour exercise period, the STAI was readministered to each subject, and a second fingerprint was taken to measure the number of open sweat pores. Results showed a significant decrease in both psychological stress as measured by the STAI and in physiological stress as measured by the PSI. (JM)