The serum levels of ACTH, PRL, GH, somatomedin-C and cortisol (also in saliva) and urinary 17-OHCS excretion were investigated in 37 acromegalic males after radiotherapy. According to bromocriptine test (BC) 20 subject were classified as responders, and 17 as non-responders. ACTH concentration was normal in all acromegalic patients and remained unchanged after BC administration. Mean 24-h level of serum total cortisol was lower in untreated patients and it increased after BC treatment only in responders. No disturbances in circadian rhythm of free cortisol were observed in any of patients. A significantly elevated excretion of 17-OHCS was found in responders before and in non-responders before and after BC administration. In untreated responders significantly increased levels of GH were found which decreased significantly after bromocriptine. In non-responders no difference was found between the values before and after BC, both being significantly higher than those in controls. In both groups of patients significantly increased levels of PRL were observed which after BC decreased to the control values. The levels of somatomedin-C were changing in parallel to those of GH described above.