Establishment of threshold CMV and HIV load values associated with CMV disease would facilitate identification of HIV-infected individuals truly at risk for CMV disease in whom targeted prophylactic interventions to prevent CMV disease would be indicated. These studies would also further the understanding of the natural history of CMV disease within the context of AIDS. Natural history studies conducted prior to the advent of highly active antiretroviral therapy (HAART; i.e., 3-drug regimens that include HIV reverse transcriptase and protease inhibitors) have demonstrated that the risk for developing CMV disease increases with progression of HIV disease and with declining CD4 counts. Presently the need exists to define the natural history of CMV disease in patients with AIDS within the context of HAART.