Highly-purified non-transformed rat liver [3H]triamcinolone acetonide-receptor complex was shown to be covalently adsorbed on activated thiol sepharose 4B, a reactive sulfhydryl matrice. Elution by mercaptoethanol in excess and inhibition of binding by previous treatment of the complex with N-ethylmaleimide clearly demonstrated the specificity of the binding by thiol disulfide interchange. The transformed [3H]triamcinolone acetonide-receptor complex, partially purified by DNA-cellulose chromatography, was also retained on activated thiol sepharose 4B. The physicochemical characteristics of both the transformed and non-transformed glucocorticoid receptor complexes eluted from the covalent chromatography column were studied by HP size exclusion chromatography on a TSK G 3000 SW column and were found to be identical to those of the starting complexes. These results provide direct evidence for accessible sulfhydryl groups on the glucocorticoid receptor complex surface, probably distinct from the steroid binding essential sulfhydryl group.