This study tested the effects of post-session wheel running on within-session changes in operant responding. Lever-pressing by six rats was reinforced by a food pellet under a continuous reinforcement (CRF) schedule in 30-min sessions. Two different flavored food pellets were used as reinforcers. In the wheel conditions, 30-min operant-sessions with one of the flavored pellets were followed by 30-min free-wheel running sessions. Meanwhile, in the home conditions, rats' operant responding was reinforced by the other flavored pellets during 30-min operant-sessions, and the rats were then returned to their homecages. All rats were exposed to 4 wheel and 4 homecage sessions. Operant responding was lowered during the wheel conditions. However, post-session running did not alter the within-session pattern of operant responding. These effects were practically identical to the effects of drug-induced taste-aversion learning on within-session changes in operant responding, suggesting similar mechanisms in both taste-aversion preparations.