This is a competitive renewal of a training program in Developmental Hematology in the Department of Pediatrics at Washington University School of Medicine. The program will provide pediatric physicians (M.D.'s or M.D., Ph.D.'s) with postdoctoral research experience with the long-term goal of producing independent investigators capable of making important contributions to biomedical research. Trainees will be second- and third-year fellows recruited from the Hematology-Oncology fellowship program in the Department of Pediatrics at Washington University School of Medicine. This pool of fellows includes many qualified applicants with backgrounds in hematology research. Trainees will participate in a formal seminar series that includes a discussion of current research in developmental hematology, along with didactic sessions in statistics, design of research, and the ethical conduct of research. Trainees may perform their postdoctoral research in a wide range of laboratories at Washington University, provided the research is relevant to the field of developmental hematology. It is anticipated that this award will support two new trainees per year for the duration of two years. Alan L. Schwartz, M.D., Ph.D., will serve as Program Director. The continued support of this program will help to close the gap between basic developmental biologists and pediatrician clinicians.