The goals of the University of Chicago Cancer Research Center Flow Cytometry Facility are (1) to provide to UCCRC investigators the means to analyze and preparatively sort individual cell populations based on up to 5 distinct parameters (size, light scatter, red fluorescence, orange fluorescence, and green fluorescence); (2) to provide expertise in DNA analysis, signal transduction (calcium influx) analysis and cell surface phenotypic analysis and (3) to study subcellular organelles using either fluorescinated antibody probes or, in the case of cell cycle analysis, fluorochrome chemicals. Our ability to preparatively sort cells on a daily basis provides a unique resource to the Cancer Center community for isolating individual cell populations. Because of the extensive use of this facility in the past, we anticipate that it will have continued high use in the future.