SUMMARY/ABSTRACT This proposal is a request to purchase and install collapsible pen housing for groups of nonhuman primates that support the NIH priorities for HIV-related research. HIV-related research often involves long term housing of macaques that can last for up to years. Currently these animals are housed in pairs in socialization cages. To improve socialization opportunities, provide a more complex housing environment, and increase enrichment we aim to institute group housing in pens for animals on HIV/AIDS projects. Housing these animals in pens rather than individual cages improves overall animal welfare in two ways: Socialization in groups provides significantly improved psychological well-being when compared to single housing or even pair housing, and the increased total space (horizontal and vertical) in pens compared to cages improves both physical and psychological well- being. One challenge to housing research animals in pens is the need to access animals for research procedures or sampling. The proposed pens are designed to attach to one-over-one caging enclosures on both sides. Animals will be trained to enter these enclosures voluntarily. Once within the enclosures, noninvasive samples may be obtained voluntarily, or animals may be sedated for other procedures as required.