We request an Affymetrix GeneChip Scanner 3000 System to complete our state of the art microarray core facility at the Johns Hopkins University School of Medicine. This system is the only piece of equipment that allows the processing and scanning of Affymetrix's new high density GeneChip arrays, which contain comprehensive whole-genome information for the human, murine, or rat genomes in a single microarray. The scanner offers advanced design improvements of speed, minimization of space, and automation of microarray scanning procedures. It provides a consistent scanner-to-scanner overall biological performance, improving data integrity and very importantly, consistent data sharing between researchers. The accessories of the scanner included in this proposal are a workstation, with the new software and new operating system, a 48-array scanner autoloader carrousel, and a fluidics station to support the high microarray throughput processed at the microarray core. These accessories are needed for the full operability of the scanner at the core. This scanner will be located in our centralized core facility within the basic sciences and will be supervised and maintained by our expert and experienced microarray core staff and management. The system will serve a large NIH-funded scientific community of over 130 users from multiple departments throughout the Johns Hopkins University.