Patients are divided into 3 groups. Group A consists of patients currently enrolled in or currently being followed in an ongoing qualifying study (see Purpose for CPCRA trials which qualify). Group B consists of patients previously enrolled in but not currently being followed in a qualifying study. Group C consists of antiretroviral-naive patients not enrolling in a qualifying study (i.e., patients starting treatment outside the FIRST study or patients deferring treatment). Patients in Group A undergo monitoring of selected clinical and laboratory parameters (including plasma HIV RNA levels and CD4 cell counts) once every 4 weeks beginning after completion of all follow-up appointments for all other protocols in which they were enrolled. Patients in Groups B and C undergo monitoring of selected clinical and laboratory parameters (including plasma HIV RNA levels and CD4 cell counts) once every 4 months. Patients are followed for at least 5 years. [AS PER AMENDMENT 2/28/01: Patients who are not being followed in a qualifying protocol and are antiretroviral naive at enrollment or were previously enrolled in the FIRST (CPCRA 058) protocol undergo blood draws at enrollment and then annually for measurement of plasma HIV levels by a CPCRA-approved laboratory and future CPCRA-approved, HIV-related research. Patients who relocate to a non-CPCRA affiliated site are asked to sign a consent for ongoing release (every 4 months) of their medical records from their new health care provider to the CPCRA.]