The standard of care for second-line HIV therapy in patients who have failed a first-line NNRTI-based regimen is to combine a boosted protease inhibitor (bPI) with two (new) NRTIs. However, patients failing first-line therapy in roll-out programmes often have extensive NRTI resistance mutations that may compromise the efficacy of the NRTI drugs used in second-line therapy and it is likely that the virological potency of the second-line regimen is mostly due to the bPI. It is possible that the contribution of the NRTI drugs to efficacy may be outweighed by additional toxicity and cost. It is also possible that replacing the NRTI drugs with a new class of drug (integrase inhibitors) will improve outcome from second-line therapy, although if the boosted protease inhibitor alone is providing close to optimal response, incremental gains from adding a new class may be small.