This Program Physician Scientist Award (PPSA) application seeks to provide postdoctoral research experience and scholarly research training of pediatrician-scientists in molecular biology, protein chemistry,l cell biology or other basic disciplines so as to render Trainees independent investigators making substantive contributions to biomedical research. The principal features of the program ae: [1] emphasis on the training of pediatric physician-scientists; [2] inclusion of MD-PhD's who require scientific retraining as well as MD's; [3] individually designed clinical and research training program; [4] accessibility to wide range of research laboratories in Boston biomedical community; [5] commitment to continue training even if Trainee initially unsuccessful; and [6] expectation that Trainee will join Harvard Medical School Faculty in tenure track position. Trainees will be recruited from the Hematology/Oncology and Nephrology division Fellows and from Fellows doing combined fellowships with these two divisions.