Twenty-three anemic children with end-stage renal failure (ESRD), aged 0.1-19.0 years (X +/- SD, 8.3 +/- 5.7 years), were treated with intravenous recombinant human erythropoietin (rHuEPO). Eleven were on conservative treatment and their estimated glomerular filtration rate (EGFR) was 11.8 +/- 3.8 ml/min/1.73 m2; 7 were on continuous ambulatory peritoneal dialysis (CAPD) and 5 on chronic hemodialysis. rHuEPO was given once a week in predialysis and CAPD children and thrice weekly in patients on hemodialysis. The initial dose of 50 U/kg/week was increased gradually up to a target hemoglobin of 10-12 g/dl. After 4.3 +/- 1.3 months of treatment, hemoglobin increased from 7.4 +/- 1.3 to 10.7 +/- 1.4 g/dl (p less than 0.001). An hemoglobin concentration of 11.4 +/- 0.9 g/dl was maintained with a rHuEPO dose of 289 +/- 86 U/kg/week. The response was similar in predialysis, CAPD, and hemodialysis children. No change in renal function was observed in predialysis children, EGFR being 11.8 +/- 3.8 and 10.8 +/- 1.7 ml/min/1.73 m2, before and after rHuEPO therapy. All children improved appetite, physical activity, and the sense of well-being. Four developed mild hypertension that was easily controlled with antihypertensive therapy. Heparin dose had to be increased during the hemodialysis sessions to avoid clotting of the filter. Serum calcium increased from 9.9 +/- 0.9 to 10.5 +/- 0.9 mg/dl (p less than 0.001). Serum aluminium levels also increased from 65 +/- 17 to 100 +/- 15 micrograms/l, p less than 0.01. A linear correlation (r = 0.58, p less than 0.01) between aluminium levels and rHuEPO dose was found.(ABSTRACT TRUNCATED AT 250 WORDS)