Human pituitary glands and pituitary adenomas, obtained by surgery or at autopsy, have been stained with lead hematoxylin and the results were compared with those of other histochemical procedures, including the immunoperoxidase technique. Lead hematoxylin positivity was found in the cytoplasm of melanocorticotroph, thyrotroph as well as gonadotroph cells, indicating that lead hematoxylin has no selective affinity for melanocorticotroph cells. Lead hematoxylin positive cells also stained with the PAS technique. Lead hematoxylin positivity was not revealed in growth hormone cells or in prolactin cells. Basophilic adenomas, composed of melanocorticotroph cells and associated with Cushing's disease or with Nelson's syndrome or unaccompanied by hormonal hypersecretion, showed intense lead hematoxylin positivity. Thus, no correlation was evident between lead hematoxylin positivity and secretory activity. Acidophilic or chromophobic adenomas consisting of growth hormone cells, prolactin cells, stem cells, undifferentiated cells or oncocytes, however, were negative. It can be concluded that the lead hematoxylin staining techniques a reliable, easy and reproducible histochemical method, and its use can be recommended in studies related to adenohypophysial cytology.