This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This study will try to learn more about physical and mental effects of HIV on the brain and determine who may be at a higher risk of difficulties related to the brain. The study will observe the amount of different brain chemicals, and the size of different brain regions by doing an imagining test called magnetic resonance spectroscopy. Results from this test will be compared to neurological and neuropsychological tests completed during this study. Eligible subjects already enrolled in the California NeuroAIDS Tissue Network study will be asked if they are willing to participate in this study. If willing, they will have MRS only performed. The data that is being collected for the CNTN study will be used to compare with the MRS. A screening visit will be done, during which their medication and medical history will be taken, and one tablespoon of blood will be taken for routine laboratory tests. Women will have a pregnancy test and will not participate if pregnant.