Thirteen male, Long-Evans rats were trained to press a lever to postpone a brief electric shock. Each rat was subjected to several different doses of chlorpromazine, d-amphetamine, atropine and benactyzine, and then tested for four hours under a mixed schedule of extinction and nondiscriminated avoidance behavior. In comparison with interspersed control sessions, chlorpromazine produced a consistent depression. Amphetamine increased response rates at moderate doses, and led to severely toxic reactions at higher doses. The three anticholinergic drugs produced qualitatively similar reactions within rats, but very different patterns of response between rats. Most animals showed higher response rates, but a few were depressed.