This study, aimed at clarifying some methodological problems of the hCRF stimulation test, was performed on 12 healthy male volunteers. ACTH and cortisol increases after 30 min and their maximum increase proved to be highly reliable response parameters for the net area under the response curve of both hormones. An influence of baseline hormone values on the maximum response was apparent for cortisol but not for ACTH. Cortisol, but not ACTH, revealed a stable test-retest reliability. There were no correlations between ACTH and cortisol responses to hCRF.