The effects of dorsal, ventral, and near-total hippocampal lesions upon both rhythmic and stress-induced corticosterone secretion in adult male rats were examined. All hippocampally-damaged, cortically-damaged, and intact rats showed rhythmic corticosterone secretion as measured in 4 blood samples for each animal taken at 6-h intervals at least 1 week apart. There were no significant differences among the groups. In addition, there were no significant differences in the amount of stress-induced corticosterone across experimental groups.