We have evaluated the efficacy of administering recombinant human erythropoietin (rh-Epo) to 11 healthy bone marrow donors weighing less than 30 kg. Three weeks before harvesting, the donors received 100 units/kg/day rh-Epo subcutaneously and oral iron supplementation (2.5 mg/kg twice daily). Six children with hematocrit values below the normal ranges for their ages after bone marrow harvesting received 150 units/kg rh-Epo three times a week for 2 weeks and oral iron supplementation at the same dose. No rh-Epo side-effects were observed. Hematocrit values before harvesting increased to between 5.7 and 18.5 (mean 10.6 +/- 1.2) above the baseline values (P = 0.0001). Hematocrit after harvesting decreased to between 4 and 19.5% (mean, 11.1) below the day 0 pre-harvest values. On day + 15 all but one patient had a hematocrit value > or = baseline value. No patient required transfusion during or after bone marrow harvest. Our results show that rh-Epo administration can avoid transfusion and has no side-effects in low weight child bone marrow donors.