Research has shown that aerobic exercise is effective in alleviating depression. However, the contention that aerobic exercise similarly has an enduring beneficial psychological effect on the mood of normal, non-depressed individuals has not been verified. Research examining the effects of exercise on normal mood has yielded inconsistent findings, due in part to methodological shortcomings. The present study attempted to rectify these methodological difficulties and evaluated the effect of 13 weeks of aerobic exercise on the mood of normal, non-depressed men and women. Groups intended to be non-aerobic and waiting list controls were included in the design, as were a stratified random sampling procedure, measurement of physical fitness, and a seven-day pre/post-program assessment period for both positive and negative mood. Results indicated that, although subjects demonstrated significant improvement in physical fitness, there were no significant changes in either positive or negative mood. Thus, in contrast to effects with clinical depressives, exercise does not appear to have any long-term beneficial effect on the mood of non-depressed individuals selected from a normal, i.e. non-clinical, population.