The overall objectives of the program are to develop biodosimetry and effective countermeasures for radiation exposure. All projects will require access to different radiation sources. The Radiation Resource Core will provide dosimetry, radiobiology support, and access to different types of radiation sources including both low and high LET radiations. The Core will be responsible for advising on appropriate radiation sources to use and will coordinate irradiation protocols. The Core will directly supervise any gamma-ray exposures that use the J.L. Sheperd Model 81-14A Cs-137 irradiator. This irradiator has the capability of providing both whole body and partial body exposures of small animals. The Core wilil also oversee the irradiations with the Varian CLINAC 4 at the Fred Hutchinson Cancer Research Center and will provide access to alpha radiation. The alpha source will be At-211, which is generated in the medical cyclotron in the Department of Radiation Oncology at the University of Washington.