The development of effective HIV vaccines and other prevention strategies relies on the use of nonhuman primates (NHPs) in preclinical studies. To meet this need, the Simian Vaccine Evaluation Units (SVEUs) provide NHP resources that primarily support preclinical evaluation of AIDS vaccines and prevention modalities. The SVEU program will provide NIAID the ability to evaluate candidate AIDS vaccines using NHP models in which thorough evaluations of systemic and mucosal immune responses can be conducted, vaccine efficacy can easily be tested, correlates of reduced risk of virus acquisition can be identified, and approaches to enhance immunogenicity and efficacy of clinical vaccines can be conducted. The SVEUs will provide a responsive, flexible vaccine resource that is available to NIH-supported researchers and can support all stages of AIDS vaccine research, from preclinical evaluation or clinical testing of candidate AIDS vaccines, with the objective of identifying a vaccine that will generate immune responses able to prevent or control viral infection. The scope of the SVEUs includes housing and maintenance of NHPs, the conduct of studies supporting AIDS prevention research, with an emphasis on AIDS vaccines, support of a NHP breeding colony, and general administration and management of these activities.