The mission of the OSUCCC Proteomics Shared Resource (PSR) is to advance the quality of cancer research while increasing productivity of OSUCCC members at reduced costs through providing high quality instrumentation and expert resources. The PSR provides instrumentation, scientific expertise and shared research services needed for the identification of proteins, protein modifications and protein biomarkers. The methods in proteomic analysis supported by the PSR include protein extraction from biopsies or ce cu tures, 2- dimensional protein separation, protein identification by MALDI-TOF and electrospray ionization coupled with liquid chromatography (LC) mass spectrometry and database searching, protein quantification through image analysis of 2D-gels and protein pattern recognition by SELDI-TOF mass spectrometry for serum analyses. The PSR is designed to provide affordable and high quality service in each of these areas, based on a cost-effective charge-back system. Under the leadership of Dr. Ming-Daw Tsai, the PSR facility provides technical expertise for OSUCCC researchers to submit samples for proteomic analysis as well as a collaborative environment for researchers to discuss with the PSR staff on how to solve a research problem using cutting-edge technology so that these researchers can more effectively and efficiently solve problems of chemical and protein biomarker and diagnosis on cancer samp es and research projects. Since 1999, over $3.8 M of institutional support has been invested in the development of the PSR, with almost half of that amount supporting the purchase of state-of-the-part instrumentation. Although relatively new, the PSR has shown an increasing usage by OSUCCC members, now exceeding 30 members representing all 6 of the OSUCCC research programs. At present, OSUCCC member usage of the PSR represents approximately one-third of the total usage of the facility. Based on historical growth as well as planned growth from new recruitment efforts within the OSUCCC and the role proteomics is beginning to play in profiling the cancer cell, it is projected that OSUCCC members will represent more than 50% of the total PSR usage in the new project period. We now request CCSG funding for the PSR that will provide `23% of the total support for this important full Shared Resource over the next five years.