The present study investigated the role of corticotropin-releasing factor (CRF) in the lateral septum in modulating the memory process and in regulation of the rearing response in rats. Rats were bilaterally cannulated in the lateral septum and CRF was injected right after training of an inhibitory avoidance task. Retention performance and rearing measure were conducted 24 hr later. In another experiment, CRF was also injected into the lateral septum and rearing response measured immediately afterwards. Results indicated that CRF, at moderate doses, markedly enhanced memory retention and decreased rearing response in rats. The latter effect was no longer observed 24 hr after CRF injection. These findings support the notion that the lateral septum is involved in the memory process and emotional expression. These results, together with earlier reports, also suggest that CRF probably produces a consistent facilitatory effect upon memory consolidation and inhibitory effect upon exploration within the limbic system in rats.