ABSTRACT Overview: The Flow Cytometry Shared Resource (FCSR) has served as a cornerstone for UCCC research since 1988, supporting basic, translational, and clinical cancer investigators seeking to use cytometry-based technologies (flow cytometry, FACS and mass cytometry or CyTOF). These technologies allow the identification, quantification and purification of cells based on gene and protein expression. Services and Expertise: The FCSR provides the equipment and staff expertise to support application of, and education in, a range of cytometry-based methods. The FCSR mission is supported by a highly knowledgeable staff with >80 years combined expertise in cytometry-based research. Equipment: The FCSR houses 4 cell sorters, 3 conventional flow cytometers, 1 spectral flow cytometer, and a Helios mass cytometer, enabling cytometry-based research from simple to high-end analysis. Management: The FCSR is a Cancer Center-managed SR, led by Clambey (THI), an immunologist who frequently leverages flow and mass cytometry-based studies to investigate mechanisms of immune control or failure; and FCSR manager, Acosta, who has >21 years of expertise in flow cytometry in academia and industry. Use of Services: Since 2016, the FCSR has provided support to 137 UCCC researchers, accounting for 67% of total revenues and resulting in 125 cancer-related publications. FCSR services are used by UCCC members from all four programs. Operating Budget: CCSG funds represent 15% of the operating budget, with the remainder from chargebacks (60%) and institutional support (25%). Innovation and Developments: The FCSR continues to innovate and expand services to address evolving user needs and new opportunities in cytometry-based research. In the most recent funding period, the FCSR added two new services - investigator-operated cell sorting and spectral flow cytometry; established a CyTOF antibody bank to reduce the barrier to entry for investigators interested in using CyTOF; and initiated remote investigator-operated flow cytometer access to ensure continued service during the COVID-19 pandemic. Consultation and Education: The FCSR uses its experience and knowledge to consult with, and educate, investigators in the use of cytometry-based research, conducting >800 consultations and >300 training session since 2016. Education is further promoted through one-on-one meetings, user groups, and seminars. Future Directions: The FCSR will continue to provide robust support for cytometry-based research by UCCC members, through acquisition and deployment of cutting-edge equipment, development of highly experienced staff, and an ongoing commitment to user education in cytometry-based research and new research opportunities. In order for these services to remain competitive, the FCSR will further: i) update cell sorting capacity through acquisition of a high- parameter, user-operated cell sorter with spectral sorting capacity and a built-in biosafety cabinet, a...