This study investigated preferred exercise intensity and accompanying HR and perceived exertion in college students (N = 55) during a 15-minute exercise session. To understand possible benefits of exercising at a preferred intensity, acute mood change after the brief exercise session and the influence of exercise enjoyment on mood improvement also were examined. Prior to exercising, students recorded their resting heart rate and completed a trait measure of exercise enjoyment using the Physical Activity Enjoyment Scale (PACES). They completed the Profile of Mood States (POMS) before and after jogging at a preferred intensity. When exercising at their preferred exercise intensity, undergraduate students exercised at 78.1% of their heart rate reserve (HRR), a hard intensity level. However, their perceived exercise intensity as reflected by their mean RPE of 12.4 was a light to moderate intensity. Results of a MANOVA on the six POMS subscales indicated significant and desirable mood changes after jogging. There was no evidence that mood enhancement was related to participants 'general enjoyment of exercise. In conclusion, as little as 15 minutes of preferred intensity exercise was associated with desirable mood changes, and students were exercising at a higher exercise intensity than they perceived. [ABSTRACT FROM AUTHOR]