This protocol is an exploratory study of HIV expression in patients who are receiving highly active antiviral therapy and who have low viral loads below or near the current limit of detection (50 copies/ml plasma). Recent studies have suggested that patients with suppressed viral loads in this low range have continued HIV expression, but the amount and the origin of this virus remains unknown. The amount of virus expression in plasma is uncertain because the current viral load assays are imprecise in the cutoff range of 50-75 copies/ml plasma. The origin of the HIV found at low viral loads detected is unknown as well; two possible sources of virus include expression from long-lived reservoirs of infected cells, and low level spreading infection to uninfected cells. Determining the origin of HIV expression has clinical importance; currently available HIV drug therapy will have little effect on HIV expression from established reservoirs, but more potent HIV therapy could potentially inhibit a spreading HIV infection.