The efficacy of recombinant human growth hormone (rGH) was assessed in five pediatric allograft recipients with severe growth retardation despite successful renal transplants. rGH 0.05 mg/kg per dose was given six times weekly by subcutaneous injection to five prepubertal children (mean age 15.2 +/- 2.0 years) all of whom had bone ages less than or equal to 12 years (10.0 +/- 1.4 years), a height standard deviation score of less than -2.5 (-4.9 +/- 1.5), no evidence of catch-up growth, a calculated glomerular filtration rate (GFR) of more than 40 ml/min per 1.73 m2 (51 +/- 6.8 ml/min per 1.73 m2), and stable renal function on alternate-day prednisone (16.7 +/- 2.6 mg/m2 per dose). Growth hormone profiles were abnormal in all children before treatment. rGH administration led to a significant increase in both growth rate (3.5 +/- 1.6 cm/year pre therapy, 8.5 +/- 1.4 cm/year post therapy, P less than 0.001) and percentage of expected growth velocity for bone age (67 +/- 31% pre therapy, 163 +/- 27% post therapy, P less than 0.001) with evidence of true catch-up growth. During the study period, three children had the appearance of secondary sexual characteristics, and one had premature advancement of his bone age. GFR decreased in three children, and in one rGH was discontinued due to a steady rise in serum creatinine. No significant changes were seen in serum calcium, phosphorus, cholesterol, triglycerides, glucose, or thyroid function, although a significant increase in alkaline phosphatase was found. In summary, growth-retarded pediatric renal allograft recipients may have abnormal endogenous GH production and respond favorably to rGH.(ABSTRACT TRUNCATED AT 250 WORDS)