We studied short- and long-term responses to growth hormone (GH) treatment and adverse medical events (AE) in 488 patients with craniopharyngioma who were entered into the Kabi International Growth Study (KIGS). First-year growth response and responsiveness (n = 394) were similar to those seen in children with idiopathic GH deficiency. The growth response over 5 years (n = 152) was unaffected by the recurrence of tumour and prior tumour management, but was greater in those receiving thyroxine. Mean height standard deviation scores (SDS) at the end of GH treatment (n = 129) was -0.7+/-1.2, and 79% achieved a height over -2 SD of target height, with evidence of further growth potential. Final height SDS correlated positively with height SDS at the start of treatment and with target height SDS, whereas gain in height SDS was inversely correlated with height SDS and bone age at the start of GH treatment. The rate of recurrence of tumour, 0.045/treatment year, was greater in those who had been treated with surgery alone compared to surgery and cranial irradiation. Other AE included headaches, fluid retention and convulsions occurring at rates of 0.025, 0.005 and 0.004/treatment year, respectively. We concluded that GH treatment is safe and effective in children with craniopharyngioma and provide data for counselling of parents about outcome during GH treatment.