The purpose of this study is to identify the frequency and severity of growth hormone deficiency in bone marrow transplant survivors by prospective evaluation of growth hormone stimulation by the glucagon stimulation test at 6 months, 12 months and annually thereafter. These children are at high risk for pituitary dysfunction due to intensive chemotherapy and total body irradiation and, in some cases, irradiation to the CNS. Early detection may permit intervention to prevent growth retardation.