In order to investigate influences of corticotropin-releasing hormone (CRH) and corticotropin fragment (adrenocorticotropic hormone, ACTH, 4–9) on auditory perception processes, 10 subjects received either a placebo (sodium chloride 0.9%), CRH (100 µg) or ACTH 4–9 (Hoe 427, 300 µg) intravenously on different days. Late auditory evoked potentials (AEP) were computed and further analyzed using the brain electric source analysis method. As expected, CRH administration was followed by a rise in plasma cortisol and ACTH concentrations, whereas the injection of the ACTH 4–9 fragment did not alter plasma cortisol concentrations. In contrast to these different hormonal responses, both CRH and ACTH 4–9 modulated AEP in a similar manner, differing in quantity rather than in quality. The changes in AEP after the administration of ACTH 4–9 were most likely induced by a direct CNS action, whereas for the CRH effects, an indirect mechanism through the release of endogenous ACTH must be