Given that most studies to date examined the connection between exercise and affect without considering the participants' preferred exercise workload, in this research the affective-benefits of jogging or running at a participant-selected pace were investigated in a pilot field and a laboratory experiment. Ninety-six male and female students (19.5 yrs) took part in the pilot field experiment whereas 32 women (20.3 yrs) completed the laboratory experiment. In both experiments, the participants ran/jogged for 20 minutes at a self-selected pace. They completed an abbreviated version of a 'right now form' of the Profile of Mood States (POMS - Grove and Prapavessis, 1992) inventory before and after exercise. In both experiments all dependent measures changed significantly from pre- to post-exercise, except 'fatigue' and 'vigor' that did not change in the laboratory. Total mood disturbance (TMD) decreased significantly in both experiments (68% and 89%). No significant correlations were found between exercise intensity (expressed as percent (%) of maximal heart rate reserve) and the magnitude of changes seen in the dependent measures. It is concluded that exercising at a self-selected workload yields positive changes in affect that are unrelated to exercise intensity. These results suggest that the physiological theories linking exercise with positive changes in affect, in which exercise intensity is instrumental, could not account for the acute affective benefits of exercise. It is proposed that a 'cognitive appraisal hypothesis' may be more appropriate in explaining the acute affective benefits of exercise