The Immunology Quality Assessment Program (IQA) is a flexible resource, designed to help investigators assess the quality of immunologic assays performed on subjects enrolled in NIAID-sponsored or collaborative HIV/AIDS studies, and to help with standardization and implementation of new immunologic assays in such studies. The IQA facilitates research to identify and quantify the sources of variability (intra-assay, intra- subject) in immunologic assays used for the monitoring of subjects in research studies (e.g. clinical trials, epidemiologic cohorts) so that this information can be used to improve study design and analysis. Specifically, the IQA Contractor obtains, characterizes, documents, stores and distributes coded quality control materials, such as whole blood, plasma and cells from HIV positive and negative donors with known immunological and virological profiles, and periodically provides these materials to designated laboratories for the purpose of monitoring and evaluating their ability to perform immunological measurements. When appropriate, investigators formulate criteria for acceptable assay performance and laboratories are being evaluated and graded. In addition, quality control materials and other reagents are provided to designated laboratories in order to facilitate comparative evaluations of instruments, reagents, and methods, and for the purpose of identifying and quantifying sources of variability in various immunological assays. Statistical analyses are performed on data received from participating laboratories and results are shared with investigators.