We studied the effect of recombinant human growth hormone treatment on five boys, aged 4.6 +/- 1.8 years, who had chronic renal failure secondary to congenital renal diseases (mean creatinine clearance (+/- SD): 18.3 +/- 6.3 ml/min/1.73 m2 (0.32 +/- 0.11 ml/sec/1.73 m2]. Patients received 0.125 mg/kg of growth hormone three times per week for 1 year. Before beginning treatment, the children had a mean annual growth velocity of 4.9 +/- 1.4 cm/yr (range 3.0 to 6.3 cm/yr), with a mean standard deviation score for a height of -2.98 +/- 0.73 (range -2.16 to -3.59). At the end of therapy, the mean growth velocity had increased to 8.9 +/- 1.2 cm/yr (range 7.5 to 10.7 cm/yr), and the mean height standard deviation score improved to -2.36 +/- 0.83 (range -1.15 to -3.18). Bone age advancement was consistent with the period of growth. Routine laboratory determinations, including results of glucose tolerance testing, did not vary significantly from pretreatment levels. These preliminary data indicate that growth-retarded children with chronic renal failure can respond to exogenous growth hormone therapy with a marked acceleration in growth velocity.