We request funds to purchase an RS2000 biological x-ray irradiator (Rad Source Technologies, Alpharetta, GA) for small animal and cell irradiation to be run as a shared resource at Oregon Health &Science University (OHSU) in Portland, OR. The requested instrument will replace an aged cesium irradiator that has been in use at OHSU since 1978 and suffers from both severe mechanical and functional limitations. At least 15 PIs at OHSU have NIH-funded research projects that are critically dependent upon having a reliable irradiator. The RS2000 biological x- ray irradiator was chosen because of its reliability, excellent customer support and the fact that it can meet a larger range of research needs than the current instrument. Obtaining this machine will be of tremendous value to the research community at OHSU and will support current and future NIH-sponsored research projects.