The literature dealing with the neuronal connections of the area postrema (AP) is reviewed. Although it has been suggested that many regions of the central nervous system are directly connected with the AP, convincing evidence exists for only a few such regions. Afferent projections have been described from specific components of the vagus and glossopharyngeal nerves, and efferent connections have been reported to the nucleus tractus solitarii and to the parabrachial nuclei. In addition, an indirect projection from the AP to the dorsal motor nucleus of the vagus nerve exists. Further study is necessary to establish whether other important connections occur, and to determine if the connectivity of the AP is consistent in various species.