Recombinant human growth hormone (rhGH) is a new treatment modality for short children with chronic renal failure (CRF) prior to and during dialysis. It is difficult to analyze whether dialysis patients respond less to rhGH than children with CRF on conservative treatment because they are older and often in a pubertal age range. One hundred and eight patients were treated with 28-30 IU rhGH/kg per week for at least 1 year. We analyzed the growth response to rhGH in 56 prepubertal patients aged less than 10 years at the start of rhGH treatment; 38 children with a mean age of 6.5 +/- 2.4 years were on conservative treatment (CT) and 18 patients with a mean age of 6.5 +/- 2 years on dialysis treatment (D). Mean height velocity was 4.9 +/- 2.3 cm/year in children on CT and 4.6 +/- 1.8 cm/year in children on D. During the 1st treatment year, height velocity was 9.5 +/- 3.8 cm/year in CT patients and 7.3 +/- 1.3 cm/year in D patients (P < 0.05). The change in height was +1.1 +/- 0.8 standard deviation (SD) in CT patients and +0.5 +/- 0.4 SD in D patients (P < 0.005). During the 2nd treatment year, the change in height was again greater in CT patients (0.5 +/- 0.4 SD vs. 0.2 +/- 0.4 SD; P < 0.05). The difference in height velocity and change in height standard deviation score was also significant when a subgroup of patients was matched for sex, age, height. Height velocity and the change in height velocity during rhGH treatment were not correlated with residual renal function, the degree of anemia, or metabolic acidosis. We conclude that short children on D respond less to rhGH than short children on CT, indicating a greater insensitivity to rhGH during D treatment.