In an extensive review of the relevant literature, the author emphasizes the importance of the limbic system—the hypothalamus, amygdala, hippocampus, and septal nuclei—in the mediation and expression of emotional, motivational, sexual, and social behavior. Joseph discusses implications of this mediation for aspects of development, including the pleasure principle and primary process. He encourages continued use of the concept of “the limbic system” because of the highly interactional nature of these structures.