Summary/Abstract This is a revised competitive application for the renewal of our T32 training grant (T32 Program). The Program is located within the Children's Center for Cancer and Blood Diseases (CCCBD), which is among the largest and top-ranked pediatric oncology programs in the US. This T32 Program entitled ?Training Physician- Scientists in Pediatric Oncology? is composed of two well integrated training units, the CCCBD located on the Children's Hospital Los Angeles (CHLA) campus and the NCI funded Norris Comprehensive Cancer Center of the University of Southern California (USC-Norris) located on the Health Sciences Campus (HSC) of USC and of which the CCCBD is an integral part. The Program will provide vital support for three years of intensive interdisciplinary laboratory research training for one MD trainee selected each year from among 4-5 subspecialty oncology fellows who have been accepted from a pool of 20-30 applicants into the Pediatric Hematology-Oncology Fellowship program of the CCCBD. The final goal is to prepare them for full-time academic careers in pediatric cancer research. Trainees conduct research relevant to the biology of childhood cancer in the laboratories of 16 T32 Program Research Mentors at CHLA and USC-Norris, who have a solid track record of NIH funding (88% currently NIH funded) and mentoring accomplishments. By performing these research projects within the larger interactive environment of an NCI-funded Comprehensive Cancer Center and participating in formal and customized curricula that include career development and strong oversight by mentoring committees, trainees develop the knowledge base, critical abilities and technical skills necessary to develop into successful independent investigators. A key focus of this T32 Program is to instill the philosophy of bridging interactions between physician-scientist trainees and integrated translational research teams. In support of this aim, trainees actively participate in one of four Team Science Programs of the CCCBD (Neuroblastoma, Leukemia, Neural Tumors and Bone Marrow Transplant/Cellular Therapies). The institutional environment provides abundant resources and a rich intellectual milieu for training in research relevant to human disease and pediatric oncology. This includes core training resources, the strong faculties and programs of the CCCBD, The Saban Research Institute of CHLA and USC-Norris, and access to state of the art core facilities and equipment. This revised application requests a progressive increase in the number of positions each year from one the first year to three the third year and thereafter.