Atropine or scopolamine improved conditioned avoidance behavior for most rats which performed poorly, in spite of extensive training, in a shuttle-box procedure. As previously reported, d-amphetamine also improved performance in many of these animals, but there was no particular relationship between a rat's responses to the cholinergic blocking agents and to d-amphetamine. The effect of any one of the 3 agents was, for the most part, reversible after the drug effect had dissipated.