The inflammatory reaction of the hindpaws inducible in rats by systemic administration of the sulfonamide 6-sulfanilamidoindazole (6-SAI) is characterized by a special tolerance reaction, i.e. the paw inflammation decreases despite a continued medication of 6-SAI. We found no change of the plasma corticosterone level in 6-SAI-dosed animals, neither at the beginning of 6-SAI administration nor when the inflammation reached maximal values nor during the remission of paw swelling. Thus, a presumed regulatory increase of the endogenous glucocorticoid concentration cannot be the reason for the spontaneous remission of this special inflammatory process. Administration of the receptor antagonist RU 486 caused an increased corticosterone plasma level by about 40% but had no significant influence on paw swelling.