The concentrations of immunoreactive corticotropin-releasing factor (I-CRF) in human cerebrospinal fluid (CSF) were measured utilizing immunoaffinity chromatography and RIA in patients with no endocrine disease, patients with Cushing's disease, Nelson's syndrome, Sheehan's syndrome, Addison's disease and steroid treated patients. On high performance liquid chromatography, the elution profile and retention time of I-CRF in CSF were not identical with ovine CRF. I-CRF concentrations in CSF from patients with Cushing's disease and Sheehan's syndrome were lower than those from normal subjects, however those from patients with Nelson's syndrome and Addison's disease were within the normal range. I-CRF concentrations in CSF from patients with Cushing's disease returned to normal levels 2-9 months after pituitary adenomectomy. These results suggest that CSF I-CRF concentrations are reduced by increased plasma corticosteroid levels.