This proposal details a plan to investigate the evolutionary history of surface materials from 25143 Itokawa, the Hayabusa samples. To accomplish these goals we request two large Hayabusa samples that have already been characterized by various non-destructive measure- ments such as CT, XRD, SEM, EMPA, and SIMS. Our studies are based on the measurement of those nuclides produced in asteroidal surface materials by cosmic rays. Cosmic-ray-produced (cosmogenic) radionuclides are used to determine the duration and nature of the exposure of ma- terials to energetic particles (e.g., Reedy et al., 1983). Our goals are to understand both the fun- damental processes on the asteroidal surface and the evolutionary history of its surface materials. These processes occur over timescales spanning the present to 107 yrs into the past. They are al- so key to understanding the history of Itokawa’s surface and asteroid-meteoroid evolutionary dy- namics. To achieve our key goals, in particular reconstructing the evolutionary histories of the asteroidal surface, we propose measuring small amounts of cosmogenic radionuclides (104-105 atoms) in Hayabusa samples.