After the washout (day 42), subjects will initiate the dual NRTI/NtRTI therapy sequence for an additional 7 days. During dual NRTI/NtRTI therapy, again, four measurements for HIV RNA will be done to calculate the slope of the phase one viral decay. On day 48 and 49, serial plasma and intracellular levels of ABC + TDF will be evaluated. On Day 49 a second HIV genotype will be performed in real time. On day 49, after the second 7-day sequence, all subjects will receive EFV in addition to the ABC + TDF combination for 14 days. Afterwards, a second sample of PBMCs will be collected to evaluate for a potential induction or suppression of nucleoside transport enzymes. Since the long-term efficacy of the TDF + ABC nucleoside backbone is not yet known, TDF will be discontinued (day 63) and 3TC will be substituted. Subjects will then continue on the HAART portion of the study for an additional 46 weeks of EFV + ABC + 3TC.