Within 30 days of the screening visit, patients return to the clinic to enter the study. Patients should not eat or drink, except medications and water, for at least 8 hours prior to this visit. Upon study entry, the following are performed: a physical exam; blood draw for routine lab tests, HIV viral load, CD4 count, and repeat lactate; urinalysis; and a pregnancy test. All patients receive the following regimen through Week 48: vitamins C, E, B1, and B2. One week after starting the vitamin regimen, patients are restarted on the same antiretroviral regimen that they were receiving at the time of hyperlactatemia. Within 30 days of study entry, the patients should be on the exact same doses of antiretrovirals that they were receiving at the time of hyperlactatemia, taking into account any necessary dose escalations. Evaluations are performed at Weeks 2, 4, 6, and 8 and every 4 weeks thereafter until Week 24. After Week 24, evaluations are then performed at 8-week intervals through Week 48. Antiretrovirals are not supplied by the study.