Over twelve percent of infants born less than 1,500 grams (VLBW) sustain brain injury with subsequent developmental delay. Although various neuroprotective strategies have been evaluated, none have been successful. One promising intervention is the use of recombinant erythropoietin (Epo, also known as an erythropoiesis stimulating agent, or ESA). In addition to stimulating red cell production, Epo has been shown to be protective in the developing brain in animal models. We have preliminary data suggesting its efficacy when used in VLBW infants, who are at risk of requiring transfusions, and who are also at risk for brain hemorrhage, hypoxicischemic brain injury, and developmental delay. We are currently performing a multicentered study evaluating hematopoietic and short term developmental effects of ESAs in preterm infants randomized to receive Epo, Darbepoetin alfa (a longer acting ESA), or placebo/ control for the first 10 weeks of age (NCT00334737). The first enrolled infants will reach 42-48 months in January, 2010. While that study evaluates the safety and general short-term developmental effects of ESAs, there is an unprecedented opportunity to study long term effects of ESA in significant detail, including evaluating the long term developmental effects and the underlying mechanism of neurologic improvement with state of the art neuroimaging. This proposal seeks to evaluate longitudinal, long-term developmental effects and underlying neurologic mechanisms of ESAs administered to VLBW infants in the first 10 weeks of life. Our specific hypotheses are: