In 1981, Vale et al. isolated, sequenced and characterized a 41 amino acid ovine hypothalamic peptide. This peptide has been shown to be a very potent secretagogue for adrenocorticotropic hormone and appears to be the major physiological corticotropin releasing factor (CRF). The CRF peptide has been anatomically localized in the paraventricular nucleus of the hypothalamus. Since 1983, the nucleotide sequences encoding the ovine and rat CRF complementary DNA (cDNA) precursors as well as the human and rat CRF genes have been determined. The nucleotide analysis of the human CRF sequences also provided the first description of the structural organization of this gene including the promoter sequences and intron/exon boundaries. The rat CRF gene was isolated employing a two-step strategy. The first step was to isolate a full length CRF cDNA clone and the second step involved the use of this cDNA clone as a hybridization probe to isolate the rat CRF gene from a rat λ genomic library.