The importance of immunophenotyping to diagnosis, prognosis, therapy, ad treatment evaluation necessitates an AIDS Program-wide flow cytometry quality control program for adult and pediatric studies. The purpose of the Flow Cytometry Quality Control contract is to provide the AIDS Program with the means for evaluating and comparing results obtained by each participating site for whit blood cell counts (WBC) and T-cell subsets. Specifically, the Flow Cytometry Quality Control contract will provide means for the development of standard methodology across participating sites and for determining the accuracy and precision of the results obtained for WBC, differentials, and for T-cell subset determinations using flow cytometry. In addition, new technology, methodology, and reagents, will be identified and, if appropriate, implemented through the participating sites. The contract will also provide for technical assistance (on site and off site) to the participating sites in establishing and maintaining a quality control program. This is a pioneering effort to quality control T-cell subset analyses on a large scale, Therefore, this contract will be instrumental in determining the limits of precision and accuracy for flow cytometry technology as applied to T-cell subset analyses in a clinical research setting. To accomplish these objectives, blood from normal and HIV seropositive donors, frozen cells, and stained and unstained standards will be sent to each participating site at regular intervals. Each site will then perform routine analysis of each sample and send back the results to the central facility. The data is then entered into the data base and statistical analysis of the data is performed. The results from each shipment are compiled and analyzed to determine performance within the tolerance limits. These results, contained in the Proficiency Reports and may include graphs and charts, are presented to the Project Officer and the Flow Cytometry Advisory Committee (comprised of immunologists from participating sites, as well as ad hoc expert members) for final review and recommendations. In addition, the Proficiency Reports will contain information about each sites' performance as compared to the entire group of participants as well as to its own previous performances. Recommendations, if appropriate will be made to a participating site if the results are unacceptable or further assistance is necessary. In summary, this contract will provide the NIAID AIDS Program with a comprehensive quality control program for those hematologic and flow cytometric assays that are used in T-cell subset determinations, including new technology, methodology, and reagents as they are implemented.