Astrocytes are the most numerous cell type in the central nervous system. When cultured, these cells express a wide variety of receptors for neurotransmitters. Nonetheless, it has yet to be firmly established that adult astrocytes in situ express receptors for neurotransmitters. In this report the technique of combined receptor autoradiography and immunocytochemistry has been applied to isolated astrocytes from adult animals to examine beta-adrenergic receptor (beta-AR) expression by these cells. It is shown that fibrous and protoplasmic astrocytes isolated from adult rat cerebral cortices specifically bind the beta-AR ligand iodocyanopindolol and that this binding is inhibited by the beta-AR ligands propranolol and isoproterenol. These results indicate that at least two of the major morphological subtypes of adult astrocytes express beta-ARs.