The glucocorticoid receptor in cytosol from human brain was studied using isoelectric focussing in slabs of polyacrylamide gel. [3H]Dexamethasone was used as tracer for receptor analysis. The glucocorticoid receptor from human brain was compared to the glucocorticoid receptor in rat brain. A similar peak of radioactivity with a pI of about 6.1 was obtained by isoelectric focussing of cytosol from both human brain and rat brain. The trypsin-induced fragmentation patterns of the glucocorticoid receptor from human brain and rat brain were very similar when analyzed by isoelectric focussing. The hormone specificity of the glucocorticoid receptor in human brain and in rat brain cytosol was compared by competition experiments using unlabelled dexamethasone, betamethasone, cortisol and corticosterone as competitors. No difference between human brain and rat brain cytosol was detected. It is concluded that the hormone specificity and the protein structure of the glucocorticoid receptors in human brain and in rat brain are similar.