We evaluated the growth of children with acute leukemia who received a bone marrow transplant (BMT) after preparation with hyperfractionated total body irradiation (TBI). Seventy-two patients (27 female and 45 male patients) with acute lymphoblastic leukemia (ALL; n = 39) or acute myelogenous leukemia (AML; n = 33) who were less than 14 years of age at BMT were studied. Before BMT all had received multiagent chemotherapy and 31 had received cranial irradiation (RT). Preparation for BMT included total body irradiation (1,375 cGy [n = 37] or 1,500 cGy [n = 35]). Heights, expressed as standard deviation scores (SDS), were studied up to 4 years post-BMT. The estimated height SDS for the entire group at the time of BMT was -0.28 +/- 0.05 and decreased to -1.11 +/- 0.22 at 4 years post-BMT (P < .0001). Using a growth curve model to compare covariate groups over the period of study, we found that the loss in height SDS was most significant in those patients who received cranial RT before BMT (P = .005). The estimated height SDS for patients treated with cranial RT went from -0.52 +/- 0.20 at transplantation to -1.83 +/- 0.23 4 years later. In contrast, patients who did not receive cranial RT before BMT showed a smaller decrease in height SDS over the 4-year observation period, ie, -0.11 +/- 0.20 decreasing to -0.73 +/- 0.21. Similarly, patients with a diagnosis of ALL had a greater loss of height SDS than those with AML (P = .033). Fifteen of 18 patients tested were found to be growth hormone (GH) deficient; 9 patients were treated with GH and all showed an improvement in growth velocity (P < .0001). We conclude that (1) children with acute leukemia who have received cranial RT and subsequently undergo BMT, primarily those with ALL, are at high risk for growth failure and GH deficiency, and (2) that fractionation of TBI may have a relative sparing effect on growth.