We propose to expand the existing state-of-the-art flow cytometry core facility at Mount Sinai with a FACSVantage SE with turbosort and DIVA options (Becton Dickinson, Mountain View, CA). Flow cytometry is critical to the projects of many of the investigators at Mount Sinai. Flow cytometry has become an integral part of many different aspects of basic and applied biomedical research including cancer research, cell biology, developmental biology, hematopoiesis, immunology and microbiology. This technology involves the analysis of fluorescence and light scatter characteristics of cells, which pass through a laser beam in a laminar flow column. Flow cytometry consists of two separate, but related applications. The first, analytical flow cytometry, includes the study of the expression of surface markers, cytoplasmic markers, Ca-flux, intracellular pH, mitochondrial membrane potential, cell cycle analysis, and green fluorescent protein (GFP) expression. The second, preparative cell sorting, involves the isolation and purification of cell populations on the basis of cell surface markers, GFP expression or cell cycle status. Given the prominent role of this technology in modem science, any institution that aims to support the most advanced research programs must develop and maintain a state-of-the-art facility that provides the capacity for multiparameter analysis and cell sorting. The Mount Sinai School of Medicine has recognized the importance of this technology and initiated the development of a shared flow cytometry facility in March 1999. Although the facility is only 3 years old, it is used routinely by more than 50 investigators and is already at capacity with the existing equipment. This proposal requests funds to expand the capacity of the facility through the purchase of a FACSVantage SE with turbosort and DIVA options (Becton Dickinson, Mountain View, CA).