Treatment of medulloblastoma in children with head and spinal irradiation causes growth hormone deficiency and growth retardation. The present study deals with 45 patients presenting a follow-up time superior to 4 years; some of them having reached their final height. The mean final height is 3 standard deviations below normal mean. Growth retardation which occurred in 42 of 45 children, appears to be due to two major factors: 1) GH deficiency in 42 cases as assessed by the arginine insulin tolerance test. 2) Spinal lesions due to irradiation, causing early growth retardation and a reduced trunk length in most of these children. The response to hGH treatment (10 mg/kg/yr) was not sufficient in this group of patients.