Endocrinological function was evaluated in 31 children after successful treatment of acute lymphoblastic leukaemia. All patients had received combination chemotherapy and 12-24Gy of cranial irradiation according to the German therapy protocols BFM-81, BFM-83 and BFM-86. Height, weight, bone age and pubertal development, as well as hypothalamic-pituitary function were measured. Long-term linear growth was unaffected in all patients. However, 9 patients showed subnormal serum growth hormone levels in response to pharmacological stimulation of the pituitary. All patients had normal levels of T3 and T4, but one patient showed an increased response of thyrotropin to thyrotropin releasing hormone. All prepubertal and postpubertal children demonstrated appropriate secretion of follicle-stimulation hormone (FSH) and luteinizing hormone (LH) after stimulation with LH-releasing hormone (LH-RH). 3 pubertal girls showed adequate oestradiol levels, but abnormally high levels of gonadotropins in response to LH-RH. Sexual development was normal in two of them, but the third had a late menarche and irregular menses. The significance of these findings is discussed in the context of recommendations possibly to further reduce or completely delete prophylactic cranial irradiation.