The medical records of 123 patients treated for brain tumors at Children's Hospital and Medical Center, Seattle, Washington, between 1985 and 1987 were reviewed. The endocrinological complications of radiation therapy and the effectiveness of growth hormone (GH) replacement therapy were assessed. These were the first 2 years after synthetic GH became available. The disease pathology was confirmed at craniotomy or biopsy in 108 patients. Ninety-five children completed radiation therapy and 65 of these were alive at the time of review; these 65 children represent the study population. The most common tumor types were medulloblastoma, craniopharyngioma, and ependymoma. Endocrine evaluation was initiated with changes in the patients' growth velocity. Patient workup included skeletal x-ray films for determination of bone and analysis of thyroxin, thyroid-stimulating hormone, and somatomedin-C levels. Following 1-dopa and clonidine stimulation, provocative studies of GH levels were performed. Growth hormone failure and short stature were observed in 26 children, most commonly in the 2nd year after tumor treatment. Eight patients with GH failure were also hypothyroid. Hormone replacement therapy was initiated with recombinant GH, 0.05 mg/kg/day, and all children so treated showed an increase in height, with eight patients experiencing catch-up growth. There were no complications of therapy or tumor recurrence. Studies of baseline bone age and somatomedin-C levels on completion of radiation therapy are recommended. Comprehensive endocrine studies should follow changes in the patients' growth velocity. With early GH replacement, catch-up growth is possible and normal adult heights may be achieved.