Depression in inmates is well-documented; however, the efficacy of any specific, nonpharmacological intervention for depression in this population was not found in a literature review. The emotional benefits of regular, aerobic exercise have been reported previously. Both experimental and epidemiological studies have documented the positive effects of exercise on mood. To test the effects of aerobic exercise on depression in inmates, this study provided 12 weeks of organized aerobic exercise for 3 hours each week to 25 inmates from one jail; 20 inmates from another facility constituted the control group. Both groups completed the Beck Depression Inventory (BDI) twice, with a 12- week interval between tests. Decreased BDI scores for the treatment group suggest that organized aerobic exercise could be an effective primary or adjunct intervention for depression in this population. There are a number of possible explanations for the study findings. First, exercise may directly affect mood. Second, the presence of the researcher and his assistant at all exercise sessions could have decreased attrition and encouraged the subjects to continue participation in the study. Finally, the alteration in routine for the subjects may have provided sufficient enjoyment and diversion to ameliorate mild depression. 25 references