The anatomical distribution of corticotropin-releasing factor (CRF) in the central nervous system (CNS) and the wide spectrum of autonomic, behavioral, and electrophysiological effects following CRF administration has led to the suggestion that CRF may act as a stress neurotransmitter in brain. The chapter discusses the distribution of CRF receptors in the context of their correlation with immunocytochemical distribution of CRF-like immunoreactivity and the possible anatomical loci mediating the pharmacological actions of CRF in rat brain. The distribution of CRF receptors in the rat olfactory system is striking. The medial portions of the vestibular nucleus had much higher concentrations of CRF binding sites, whereas the lateral and superior aspects of this nucleus had moderate to low concentrations of autoradiographic grains. The localization of CRF receptors in certain regions of the brain stem provide an anatomical basis for some of the observed effects of CRF on autonomic function.