From 1991 to 1993, 90 children having received a kidney graft with a post-transplantation period of at least 12 months were included in a prospective study carried out in Is French pediatric centers. After informed consent and randomization, children received recombinant human growth hormone (rhGH) (Genotonorm, Pharmacia peptide hormones) 30 U/m(2) per week, either immediately on enrollment, for the treated group, or after 1 year of follow-up for the group serving as a control. After 1 year both groups were treated and we analyzed data during the subsequent years. Eighty-five children completed the 1-year study. Growth velocity was significantly increased by rhGH: 7.7 cm with a gain of +0.3 standard deviation score in the treated group versus 3.6 cm in the control group (P<0.0001) during the Ist year. Four factors predicted response to therapy: growth velocity prior to GH therapy, glomerular filtration rate (GFR) at the start, mode of corticosteroid administration, and degree of insulin resistance. After I year we observed a moderate, significant decrease in GFR in both groups. Biopsy-proven acute rejection episodes were not significantly more frequent during the Ist year in the group of patients who received rhGH: 9 in 44 versus 4 in 46 patients. The patients who rejected did not differ in terms of age, renal function at the start, and type of immunosuppression, but history of rejection before GH treatment was discriminatory: 6 of 17 children with two or more episodes had a new rejection versus 1 of 22 who had no or only one episode (P=0.01). Glucose tolerance was not modified after 1 year of GH therapy. During the subsequent years of treatment a decrease in growth velocity was noted: 5.9 cm at 2 years, 5.5 at 3 years, and 5.2 cm at 4 years. In conclusion, GH is efficient for improving growth velocity in short transplanted children, inducing clear-cut but limited catch-up growth. The risk of rejection was shown only in patients with a prior history of more than one rejection episode.