Only Specific Aim #4 in the Thrasher Foundation Abstract involves human infant study subjects. Specific Aim #4) USE THE RBC BIOTINYLATION AND MATHEMATICAL MODELING METHODOLOGIES VALIDATED IN ADULT SHEEP AND NEWBORN LAMBS TO ACCURATELY MEASURE POST-TRANSFUSION RBC KINETICS IN ANEMIC NEWBORN INFANTS TRANSFUSED WITH FRESH AUTOLOGOUS, FRESH ALLOGENEIC AND STORED ALLOGENEIC RBCS. The use of biotin, a non-toxic, non-radioactive B vitamin, to distinguish among different RBC populations simultaneously by flow cytometry is critical for accomplishing our aims and holds clear advantages over other RBC labeling methods in both safety and accuracy. In utilizing the four Specific Aims to achieve our goal of establishing more effective transfusion practices by identifying the optimal RBC transfusion product for use in anemic INFANTS.