This study utilizes a pole jump active avoidance task to investigate the effects of protein synthesis on memory formation. An extinction training procedure for this task is also described. Amnesia for extinction is produced by inhibition of protein synthesis and is also demonstrated by active responding, so it is clear that there is no general impairment sufficient to disrupt motor skill, motivation, or retrieval of stored memories. It was found that while inhibition of protein synthesis in brain for 2 hr did not produce amnesia, inhibition for 6 to 8 hr did. These results demonstrate that for both shock-motivated learning and non-shock motivated extinction learning, the duration of inhibition of protein synthesis is important in determining whether amnesia occurs. We conclude that inhibition of cerebral protein synthesis can best account for amnesia induced by anisomycin, cycloheximide, and acetoxycycloheximide.