Albino rats were trained to fear and escape from an alley with an electrified floor. They were then punished by shocks whenever they entered a distinctive area part way down the alley. For several trials the punishment facilitated the tendency to run into the punishing area. The degree of facilitation at first increased with the intensity of the punishment. After many trials, however, the punishment inhibited the running. No differences in behavior were observed in animals punished every trial as compared with those punished on every 3d trial only. Implications for various theories of learning are discussed.