HIV-1 RNA emerges in CSF early in the course of HIV disease. Studies have shown that high levels of HIV-1 RNA in CSF correlate with increased severity of dementia and worsened performance on neuropsychological tests. While combination antiretroviral treatments are potent suppressors of HIV-1 replication in plasma, the extent to which these treatments suppress viral replication in CSF is unknown. A few studies suggest that antiretroviral treatments can reduce HIV-1 RNA in CSF. However, since CSF is isolated from peripheral immune responses to HIV and antiretroviral treatment may not readily penetrate the compartment, researchers hypothesize the remaining virus will overcome the antiretroviral treatment to achieve high levels of viral replication again. This virologic failure is likely accompanied by decreased cognitive function. It is therefore critical to determine the ability of antiretroviral treatments to control HIV-1 replication in the CSF and the durability of that viral suppression.