This review has focused on the fetal erythrocyte. Fetal erythropoiesis, the production of a red cell with a shortened life-span, and the unique characteristics of this cell with respect to membrane structure and function, energy metabolism, and hemoglobin synthesis have been described. The hematologic manifestations of a variety of red cell abnormalities of structure, metabolism, and hemoglobin synthesis have been presented, as well as a discussion of the anemia of prematurity and selected nutritional disturbances that may distort this normal physiologic adaptation. We hope this review has served to further the reader's appreciation of this complicated and fascinating cell. Much more needs to be learned about the fetal erythrocyte. It is to be hoped that a fuller understanding of the fetal erythrocyte will provide insights into fetal development in general.