This is a Phase II, open-label (all people know the identity of the intervention), roll-over study (participants may go ahead and participate in another clinical study). Participants who were randomized (study medication is assigned by chance) to a etravirine (ETR) treatment arm in Phase II TMC125 feeder studies (TMC125-C203, TMC125-C209, TMC125-C223 and TMC125-C211), were treated for at least 48 weeks with etravirine, and who will derive continued benefit from etravirine therapy, as judged by the investigator, will be enrolled in this study. The final visit of the sponsor-selected Phase II ETR study will be the first (baseline) visit of this study. Approximately 300 participants will be enrolled in this study who will receive 800 mg twice daily of etravirine (formulation TF035) until the formulation 200 mg twice daily (formulation F060) is available. Once this formulation becomes available all the participants will be switched to receive F060 which will be given in combination with an investigator-selected, optimized underlying therapy (nucleotide reverse transcriptase [NRTIs] and/or allowed protease inhibitors and/or enfuvirtide). Participants will continue to receive ETR until they are no longer benefitted or this medication becomes commercially available. Safety evaluations will include assessment of adverse events, clinical laboratory tests, electrocardiogram, vital signs, and physical examination.