The acquisition of wheel running, its effects on food intake and body weight, and the effects of wheel deprivation, were examined in male rats. Running increased during the first 15 days of access, then plateaued. When wheels were unlocked after 10 days of deprivation, running was reduced, but quickly recovered to original levels. Animals first given wheel access 49 days into the study ran little, with no increase over days. Food intake dropped each time with wheel access, but recovered to control levels over 10-14 days. Wheel deprivation resulted in a temporary hyperphagia. With wheel access, weight initially dropped and was then maintained at a reduced percentage of homecage-housed animals. In male rats wheel access appears to have temporary effects on food intake, and long term effects on weight. Marked differences in the activity of same-age rats suggest that wheel running is in part a function of housing history.