Impaired growth after TBI prior to BMT has been a constant finding in children with leukemia. The growth of poor-risk neuroblastoma (NBL) survivors treated with myeloablative preparative regimens and ABMT at the Hospital for Children and Adolescents, University of Helsinki, since 1982 is reported. Two separate groups were analyzed: (1) The TBI- patients (n = 15) were conditioned with high-dose chemotherapy only. They had been treated at the age of 1.0-6.3 (mean 3.0) years and the post-ABMT follow-up time was 1.5-14.5 (mean 7.7) years. (2) The TBI+ patients (n = 16) had received TBI in addition to high-dose chemotherapy. They had been treated at the age of 1.3-4. 8 (mean 3.0) years, and the post-ABMT follow-up time was 1.5-8.0 (mean 4.7) years. The height standard deviation score (SDS) was similar for the two groups at the time of diagnosis, -0.3 +/- 1.2 (mean +/- s.d.), and at the time of ABMT, -0.7 +/- 1.1. After transplantation, the height SDS continued to decrease in the TBI+ group, the mean being -2.0 SDS at 5 years after ABMT. In the TBI-group, the mean height SDS remained within -0.7 to -0.9 to the 10 years of follow-up. Five patients received growth hormone (GH) therapy starting 2-6 years after ABMT. They all had low GH secretion in provocative tests. All showed some response to GH therapy. The mean height SDS increased 0.4 SDS during the 3 years following the start of GH therapy, while in the untreated patients a decrease of 0. 8 SDS during the corresponding time (P = 0.009) was observed. We conclude that NBL patients grow poorly following ABMT when TBI is included in the conditioning regimen, but close to normally when treated without TBI. The need for GH therapy should be evaluated early to avoid an unnecessary decrease in final height.