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Aim: To evaluate the effect of fractionated stereotactic radiotherapy (FSRT) in acromegaly in a retrospective analysis. Patients and methods: Thirty-four patients (17 females, median 43 years (range 30-74)) with acromegaly were treated with FSRT (conformal dynamic arcing, dose 54 Gy, 27-30 fractions) between January 1998 and April 2007. Thirty-two of the 34 patients had undergone transsphenoidal adenotomy, and 28 were on medical therapy before FSRT. Patients on medical therapy continued this during and after the irradiation. The treatment was gradually decreased/withdrawn after careful assessment. Results: MR scanning of the pituitary gland 34 months (median, range 11-95) after irradiation showed stable or reduced volume of the remaining tumour tissue in 31 of 34 patients (91%). Seventeen patients (50%) were biochemically controlled (normalised nadir growth hormone during OGTT and insulin-like growth factor-I (IGF-1) <+2SD) 30 months after FSRT (median, range 6-60), ten of them had true biochemical remission (off medical therapy) 30 months after FSRT (median, range 12-69). Eight of 28 patients (29%) with one or more functioning pituitary axes before irradiation developed further deficit of 1 or 2 pituitary axes 48 months (median, range 6-102) after FSRT. Twenty of 34 patients still required medical treatment for acromegaly a