Infants with chronic renal failure (CRF) are at high risk of experiencing severe growth retardation. We report a study of 12 infants with CRF who have been treated with recombinant human growth hormone (rhGH) since the age of 0.5 +/- 0.3 years. A control group comprised 15 infants with less severe CRF who were being treated during the same period, but who did not receive rhGH. Despite the infants in the rhGH group had more severe renal failure, they grew at least as well as those in the control group and experienced catch-up growth that started earlier and was more sustained; they also gained more weight. Between the age of 0.5 and 2.5 years, the height standard deviation score (HtSDS) improved from -2.0 +/- 1.2 to -0.9 +/- 0.9 in the rhGH group (p < 0.005) and from -1.6 +/- 1.6 to -1.0 +/- 1.9 in the control group (p=non significant, n.s.). The average gain in HtSDS was +1.1 +/- 0.8 in the treated group and +0.6 +/- 1.4 in the control group (p = n.s.). During the same period, the weight SDS improved from -2.2 +/- 0.9 to -0.6 +/- 1.2 (p < 0.005) and from -1.9 +/- 1.2 to -1.3 +/- 1.2 (p=n.s.) in the treatment and control groups, respectively. Nutritional intake was similar in both groups, while parathyroid hormone levels tended to increase, although not significantly, after rhGH treatment (p=n.s.). The results of this pilot study suggest that very early treatment with rhGH in patients with early-onset CRF may improve growth.