Participants had study visits at Weeks 2, 4, 8, 12, 16, 24, and every 12 weeks thereafter until the drug regimen was switched to second-line treatment. Participants then had a re-entry visit and the schedule of visits restarted. Participants were in the study between 4 and 7 years, depending on when they enrolled. All study visits included medical history, a physical exam, and blood collection. Urine collection occurred at most visits. Participants were asked to complete adherence questionnaires and PACTG participants underwent neuropsychological assessments at selected visits.