 - Clinically stable on their first or second HAART regimen. Changes while the patient HIV viral load is undetectable does not count toward the number of ART regimens used, only changes made for virologic failure for example an individual switching from an NNRTI-based regimen to an integrase inhibitor based regimen while the HIV viral load is undetectable will still be in their first regimen. Site investigator anticipates that a fully active alternative ART regimen could be constructed in the event of virologic failure on the current ART regimen. The current regimen should have no changes within 4 weeks of enrollment. Subjects must be willing to continue on current antiretroviral therapy for the duration of the study except for the duration of the 16 week analytical treatment interruption. NOTE: Subjects ART regimen must be in accordance with the Department of Health and Human Services Document Guidelines for the Use of Antiretroviral Agents in HIV-1 Infected Adults and Adolescents. 