Current guidelines for initial therapy in HIV infection recommend 2 NRTIs plus either a ritonavir boosted protease inhibitor or a non-nucleoside reverse transcriptase inhibitor (NNRTI). Recent data suggests that the rate of response to PI based therapy may be slightly compromised if the baseline CD4 count is ≤ 200/mm3 and the plasma HIV-1-RNA ≥ 100,000 copies/mL. This may not be equally apparent if ritonavir boosted protease inhibitors are used. The effect of baseline CD4 count and HIV-1-RNA levels on the antiviral efficacy of NNRTI based regimens has been less well characterized. A significant number of patients currently initiate therapy at late stages of progression, typically with baseline CD4 count is ≤ 200/mm3. In Mexico approximately 60% of patients who initiate therapy are within this range of CD4 cell counts. Currently, the two combinations recommended as preferred are with two NRTIs and either Efavirenz or Lopinavir/ritonavir, while other combinations of PIs and ritonavir are considered alternative.