The study design is a single arm treatment (all patients assigned to receive etravirine), open label (patients will know the identity of the treatments they are receiving) safety and antiviral activity of Etravirine (TMC125) in treatment-experienced, HIV infected children and adolescents 6 to 17 years of age. Etravirine is a new drug belonging to the NNRTI (a non-nucleoside reverse transcriptase inhibitor) drug class that slows down the growth of the human immunodeficiency virus (HIV). This drug has been tested for safety and effectiveness in adults, however, there is no data on the drug's long-term safety and antiviral activity in children and adolescents. This study will last for a maximum of 48 weeks. A total of 100 ptients will receive etravirine tablets based on body weight and an investigator selected optimized background regimen (OBR) of at least 2 antiretrovirals (ARVs), consisting of a boosted protease inhibitor (PI) and nucleoside reverse transcriptase inhibitor(s) (NRTI\[s\]). Use of enfuvirtide is optional. Safety will be monitored throughout the study.