Corticotropin-releasing factor (CRF) receptors were localized in the human pituitary gland by an in vitro labeling light microscopic autoradiographic technique using an 125I-labeled analog of ovine CRF substituted with norleucine and tyrosine at amino acid residues 21 and 32, respectively. Specific binding sites for CRF were observed in the anterior lobe while no specific binding sites for CRF were present in the posterior pituitary lobe. The CRF binding sites in the anterior lobe occurred in clusters which predominated in the anteromedial portion of the lobe. This pattern of localization of CRF binding sites resembles previously reported distributions of corticotrophs in anterior pituitary. These data support the physiological role of endogenous CRF in regulating hormone secretion from the anterior lobe of the human pituitary.