In conjunction with a multi-center core protocol to determine the impact of recombinant human erythropoietin (r-HuEPO) on the anemia of prematurity, this individual treatment center project is designed to determine the impact of r-HuEPO treatment on oxygen transport, oxygen delivery and overall oxygen utilization in preterm infants by serial measurement of the variables of SOT, P50, VO2, and calculation of O2 utilization in treted subjects and untreated controls and determine if there is a detectable physiologic benefit.