These experiments examined the effects of an ACTH4-9 analog (ORG 2766) on an inhibitory avoidance response in rats. Graded doses of ORG 2766 were administered either 1 hr prior to training, immediately after training, or 1 hr prior to the retention test. The animals were tested 24 hr after training. A 5.0 mg/kg dose was administered prior to training significantly facilitated acquisition of the response. ORG 2766 did not significantly affect retention when administered after training or prior to the retention test. Since ORG 2766 only affected acquisition of the response, it is suggested that the drug acts by influencing sensory, motivationl or attentional variables rather than directly affecting memory consolidation or retrieval processes.