Two theories offer possible explanations for the early decline of viral loads seen in acute HIV infection. The first is that CD4 target cell numbers are depleted, so the reduction in permissive target cells limits viral replication. A second is that the host develops an HIV-specific cytotoxic T lymphocyte (CTL) immune response that limits viral replication during the initial high viral titer. Consequently, enhanced clearance of HIV-infected cells results in a decline of plasma HIV RNA. This study examines the latter theory by characterizing viral and immune dynamics in the blood and lymph nodes of HIV-infected patients.