We investigated the rate of recurrence in acromegaly in 20 patients who were found to have a TRH and GnRH induced GH response postoperatively after primarily successful transsphenoidal selective adenomectomy in a retrospective study. All operations had been carried out by the same neurosurgeon (R.F.). Successful therapy was defined as basal GH-levels < or = 2 ng/ml and no evidence of residual tumour in the postoperative neuroradiological examination. The follow-up period ranged from 5 to 14 years (mean 7.7 years). At the last follow-up visit an OGTT was performed and SmC measured. In spite of the long-follow-up period we did not find patients with recurrent acromegaly in this investigation. We conclude that, in contrast to previous studies, a stimulation of GH in the TRH/GnRH test does not necessarily predict likely recurrence of acromegaly in patients with an adequate suppression of GH during an OGTT following operative microsurgical treatment.