The hypothesis that behavioral suppression due to punishment requires the intact activity of an inhibitory cholinergic CNS mechanism is examined in three experiments in rats and squirrel monkeys. Scopolamine hydrobromide and scopolamine methyl nitrate decreased further operant lever pressing which was suppressed by intermittent or continuous punishment, but scopolamine hydrobromide had a dose-dependent slight facilitatory effect on punished dextrose solution intake in monkeys and non-reinforced operant lever pressing in rats. d-Amphetamine enhanced non-reinforced responding drastically, and had a dose-dependent biphasie effect on intermittently punished operant lever pressing in rats and punished consummatory behavior in monkeys. Chlordiazepoxide consistently enhanced behavior which was suppressed by various punishment procedures; however, response suppression due to non-reinforcement remained unaltered by chlordiazepoxide. It was concluded that only few drug effects on behavior which is suppressed by punishment or nonreinforcement can be accounted for by the drugs' disinhibitory action on a eholinergie CNS mechanism or by the response rate dependency principle.