An 18-year old male is reported who presented with a history of a growtn spurt over the year preceding his admission. His height was above the 97th percentile, and he had incompletely developed secondary sexual characters. Pituitary evaluation demonstrated a moderately elevated level of growth hormone (hGH) not suppressible by a glucose load and not stimulable by TRH or by L-DOPA. Serum prolactin (PRL) concentration was also increased while gonadotrophin, thyroid and adrenal function were all subnormal. There was clear radiological evidence of a large pituitary tumour with suprasellar extension and transsphenoidal total hypophysectomy was performed. A mixed chromophobe and acidophilic adenoma was found and both growth hormone and prolactin were demonstrable in different cells of the tumour by the immunoperoxidase technique. Post-operatively the patient has hypopituitarism and levels of growth hormone and prolactin have remained low or undetectable after 6 months. Thus early diagnosis and surgical treatment of gigantism of this mixed hGH-PRL secreting pituitary tumour was associated with a cure, which contrasts with the unfavourable outcome of many of the patients previously reported.