The purpose of this proposal is to update the service provided by the USC Flow Cytometry Core Facility. Since 1980 a Becton- Dickinson FACS IV has been available to members of the USC Cancer Center. This service has been used by 15 NIH supported members of the Cancer Center who are involved in basic and clinical investigations. The FACS is used for analysis and purification by cell sorting, DNA and/or RNA analysis, and various two color procedures including cell cycle analysis of specific lymphocyte subsets. We are requesting replacement of worn out equipment and new modifications which have become available since 1980. This equipment consists of new lasers, a computer, and a cooling system to preserve the life of expensive lasers. With this equipment we will improve our graphic presentation of the data and we will be able to perform three color analysis of surface markers, a procedure which will enable us to define more precisely functionally specific lymphocyte subsets, and to analyze more precisely the cell cycle of specific lymphocyte subsets. This new equipment will allow us the flexibility to develop new uses for the flow cytometer as dictated by our current and future users.