An immunohistochemical investigation into the distribution of immunoreactive corticotrophin-releasing factor (IR-CRF) in the adult human pituitary stalk was carried out. Histological sections of six pituitary stalks were stained by an indirect immunoperoxidase technique, using a specific primary antiserum raised against synthetic ovine CRF. It was shown that IR-CRF is present surrounding the coiled capillaries of certain gomitoli bodies. These structures form the primary capillary beds of the portal system of blood flow supplying the anterior lobe of the pituitary gland. An investigation was made into the characteristics of the cellular elements of gomitoli bodies, as little is known of these structures. Immunocytochemical methods for epithelial cells (anticytokeratin and anti-epithelial membrane antigen), endothelial cells (factor VIII related antigen), glial cells (glial fibrillary acid protein and S100 protein) and neuroendocrine cells (neuron specific enolase) were employed, but none were positive.