This is a competitive renewal of a training grant proposal for a program designed to train radiation biologists who will have knowledge of the molecular, cellular and tissue effects of radiation. 6 predoctoral and 6 postdoctoral trainees are requested. Training will be offered in the radiation biology and associated laboratories of the Division of Oncology Research at the University of Pennsylvania School of Medicine. The program will involve formal course work, a lecture series and a journal club designed for our training needs, research seminars and conferences and laboratory research projects to be supervised by established investigators. The research projects will focus on various aspects of the currently funded research areas in the participating laboratories; for research projects, trainees will utilize techniques developed in modern biology to perform mechanistically-oriented studies in radiation biology/oncology. The research areas in which the 12 training directors and supervisors are involved are broadly based in cancer research, including molecular mechanisms of carcinogenesis and mutagenesis, molecular and cellular radiation biology, radiation chemistry and biochemistry, DNA repair processes, cancer prevention and radiation oncology. It is expected that graduates of the training program will continue with their research and academic careers in radiation biology and oncology.