Corticotropin-releasing factor (CRF) has behavioral activating effects when injected intracerebroventricularly in rats. CRF dose-dependently increased activity in a familiar photocell cage environment. This activation persisted after hypophysectomy, opiate receptor blockade, and low-dose dopamine receptor blockade, which suggests a unique mechanism of action. CRF also improved acquisition of a visual discrimination task. In aversive situations such as an open field test CRF produced behavioral changes consistent with increased emotionality. These results suggest that CRF liberated directly into the central nervous system may have a neurotropic action important for mobilizing behavioral responses to stress.