Use of the requested FACStar Plus is supported by and is an integral part of approximately twenty research projects at The Jackson Laboratory. Many of these studies have far reaching value to the biomedical research community by providing information and murine models for diseases such as diabetes, cancer and AIDS. Because The Jackson Laboratory provides these and other mouse models to laboratories world wide, animal health must be insured; therefore, strict importation rules limit the Staff's ability to perform their flow cytometry research elsewhere. The non-sorting FACScan that The Laboratory currently owns is fully utilized by routine analysis for both research and screening of new mutant stocks. Even if time were regularly available on the FACScan, many research requirements could not be fulfilled without the multiparameter analysis and sorting, dual lasers, automatic sampler for large screening projects and pulse processing capabilities of the FACStar Plus. Demand for the capabilities of the FACStar Plus is expected to increase in the future as several pending grants require the FACStar Plus and specialized computer software for such tasks as chromosome sorting, multiparameter analysis via cluster analysis and tumor analysis. The presently leased FACStar Plus includes only the bare essentials of a state-of-the-art flow cytometer. The versatility of the FACStar Plus allows the present system to be enhanced and modified for the present applications. The primary reason why the FACStar Plus was chosen over other available flow cytometers. The Laboratory fully intended to submit this application for NIH funding to purchase the FACStar Plus but required the capabilities of the FACStar Plus in the interim period to remain competitive in its biological research and continue producing the unique murine models of disease that have become so important in today's medical research. The Jackson Laboratory is committed to providing a state-of-the- art flow cytometry facility for both the current and future staff and thus submits this application for funding to complete the FACStar Plus system initiated last year.