This study was designed to examine some of the psychoneuroendocrine effects of exercise-induced emotional experiences and the mediating effects of environmental setting and subjects' attentional focus. Trained runners were tested during an outdoor run and two indoor treadmill running conditions. Excretions of catecholamines and cortisol significantly increased after all running conditions but not after a control condition. Results indicate that patterns of endocrine and concomitant emotional change through exercise differ when environmental setting and attentional focus are altered in such a way that a normally pleasant task such as running becomes tedious and negatively evaluated. These findings support the notion that setting, attention, and cognitive appraisal may alter the emotional experience associated with physical exercise.