We hypothesized that treatment of very low birth weight premature infants with r-HuEPO would increase erythrocyte incorporation and gastrointestinal absorption of iron. Infants with birth weights ≤1.25 kg and gestational ages <31 wk were randomized to receive 6 wk of 500 U of r-HuEPO/kg/wk (epo group,n= 7) or placebo (placebo group,n= 7). All infants received daily enteral supplementation with 6 mg of elemental iron per kg. An enteral test dose of a stable iron isotope,58Fe, was administered after the 1st (“early dosing”) and 4th (“late dosing”) wk of treatment. Mean (±SD) erythrocyte incorporation of the dose of58Fe administered determined 2 wk after early dosing was significantly greater in the epo group compared with the placebo group (4.4%± 1.6versus2.0 ± 1.4%,p= 0.013). In contrast, after late58Fe dosing, there was no difference between groups in incorporation (3.8 ± 1.6%versus5.5 ± 2.7%). Within the epo group, percentage erythrocyte incorporation of58Fe did not differ between early and late dosing, whereas in the placebo group it increased 3-fold (p< 0.01). Percentage absorption of58Fe was not different between the epo and placebo groups after both early dosing (30 ± 22%versus34 ± 8%) and late dosing (32 ± 9%versus31 ± 6%). Absorption of nonlabeled elemental iron and58Fe were significantly correlated with one another. The percentage of the absorbed58Fe dose incorporated into Hb was not different between groups. We conclude that, although erythropoietin treatment stimulates erythrocyte iron incorporation in premature infants, it has no effect on iron absorption at the r-HuEPO dose studied.Abbreviations: epo,erythropoietin;r-HuEPO,recombinant human erythropoietin;IR,abundance isotope ratio