The relationship of mood and exercise has been explored in a number of ways(e.g., the impact of mood on performance, the impact of exercise on mood, etc.). However, no study has experimentally manipulated mood to examine the effect of mood on physiologic variables in runners. This study examined the effect of mood manipulation on physiologic variables during submaximal exercise. Ten male, trained runners (age = 25.3 ± 5.2 yr; height = 176.2±4.8 cm; mass = 67.7±6.9 kg; body fat = 10.9±2.0%) completed a maximal oxygen uptake (VO2max) test on a treadmill. After the maximal test (59.8 ± 6.6 ml/kg/min), each subject took part in three separate submaximal tests (at a speed that elicited approximately 65% of VO2max) following one of three mood induction sessions. Each mood induction consisted of the subject reading a set of 60 cards with printed statements. Directly after the mood induction, subjects completed a Profile of Mood States(POMS) evaluation and began the submaximal test on the treadmill. Heart rate, oxygen consumption (VO2), and rating of perceived exertion (RPE) were recorded and compared across conditions using an ANOVA and post-hoc t-tests. An ANOVA indicated a significant difference between mean POMS test scores (F = 6.715, p= 0.006) suggesting that mood was successfully manipulated. Post-hoc comparisons of pre-exercise POMS scores demonstrated a significantly higher score for bad compared to good mood conditions. An ANOVA revealed a significant difference (F = 4.157, p = 0.03) for VO2 across the three mood conditions (good, 37.6±4.1; neutral, 36.3±3.6; bad, 36.3±3.3 ml/kg/min), while changes in heart rate (F = 1.76, p = 0.20) and RPE (F = 2.46, p = 0.11) were not significant. Post-hoc analysis showed that VO2 was significantly higher under the good condition when compared to the neutral mood condition (p = 0.05) and the bad mood condition (p = 0.03).