This study consists of two parts. Part A includes HIV-infected patients who enrolled in HIVNET D01.1 (infected-participants cohort of HIVNET D01) and whose HIV disease has been closely monitored and characterized. This study continues to monitor these patients with follow-up evaluations every 3 months for the first 18 months and then every 6 months thereafter. Part B includes newly HIV-infected patients. These patients are monitored with clinical and laboratory evaluations at 0, 1, 3, 6, 9, 12, and 18 months, and then every 6 months through Year 5.