Microarray Borne little more than a decade ago, microarray-based assays have emerged as a critical tool for basic, translational, and correlative clinical cancer research. The types of assays performed with this technology that enables hundreds to millions of simultaneous measurements include gene expression profiling, global analysis of single nucleotide polymorphisms, ChlP-on-chip assays of gene promoter activity, and proteomic analyses. Microarray-based assays are valuable for discovery research, helping investigators identify and characterize signal transduction pathways involved in carcinogenesis, as well as, biomarkers for cancer detection, prognosis, and treatment decision-making. Although spotted arrays are still used, especially for custom arrays and technology development, numerous array manufacturers have entered the marketplace making the technology much more cost-effective and reproducible. The mission of the Microarray Shared Resource is to provide Cancer Center investigators with high quality standard, cutting-edge, and custom microarray assays, as well as, consultation on experimental design and training/education about microarray methods. The Cancer Center Microarray Shared Resource has been in operation since September, 1999, when it began as a developmental shared resource with institutional support. Partial funding from the DC San Diego CCSG-started in April, 2001. Over the years the Microarray Shared Resource has grown to include three separate laboratories: (1) the VA GeneChip Core facility, located in VA-leased space in the UC San Diego Stein Building;(2) the Biomedical Genomics Microarray (BIOGEM) Core facility, located in the Leichtag Building on the UC San Diego La Jolla campus;and (3) the Biomarker Core laboratory, located in the Moores Cancer Center Building. The facilities and services provided these Core laboratories have been selected to be non-overlapping in order to mitigate the costs of microarray instrumentation, which frequently need upgrading for this rapidly evolving field. The confederation of these facilities is supported, in terms of organization and funding, by the administration of the Moores Cancer Center, the UCSD School of Medicine, and the San Diego Veterans Medical Research Foundation. The Microarray Resource Oversite Committee directs the operational policies and technology issues for the Facility. To date, the Facility has served the laboratories of more than 50 different Cancer Center investigators. It is anticipated that this use will continue to expand as costs for microarray assays decrease and new, planned microarray services in the Facility come online.