This volume presents the proceedings of the Fourth Annual Symposium on the Molecular Biology of Hemopoiesis, held in Reno, Nevada, November 1 and 2, 1988. Its focus on erythropoiesis represents an attempt to cover a rapidly expanding field, which has gone from elegant studies of erythro poietin physiology, to molecular biology, to clinical applications and again to physiology. The rapid development has been made possible by cloning of erythropoietin gene and the availability of recombinant hormone. The regulation of heme and its derivatives has also been aided by techniques of molecular biology; there is now a concerted effort to better understand how these enzymes contribute to proliferation, differentiation and maturation of the erythron. Globin gene derrangements have been targets of recent research in an attempt to correct the defect by genetic engineering. In the chapters of this book, several groups'expressed'their views on this subject. Finally, we analyze various regulators of erythropoiesis, both in vivo and in vitro. Dr. Richard Levere was a pioneer in many studies of heme metabolism and of erythropoiesis. He has been a generous supporter of research in this field and of our past meetings. It is only. fitting that this volume should be dedicated to him.