The effects of adrenalectomy on corticotropin-releasing factor (CRF) receptors in anterior and intermediate lobes of rat pituitary and in forebrain were examined using in vitro autoradiography with the radioiodinated analogue of ovine CRF, Nle21, [125I]Tyr32-CRF. The concentration of CRF receptors in the anterior pituitary was significantly reduced at 4 days and remained decreased at 9 weeks after adrenalectomy. In contrast, adrenalectomy did not alter CRF receptors in the intermediate lobe or in a variety of forebrain regions. The adrenalectomy-induced change in CRF receptors in the anterior pituitary was completely reversed by glucocorticoid replacement with dexamethasone. These data indicate that endogenous CRF is capable of modulating its receptor density in the anterior pituitary and suggest that different sources of CRF or other factors may be important in regulating intermediate lobe hormone secretion and neuronal activity in brain.