A control group will be used for the evaluation of the primary and secondary objectives in comparison to patients treated with raltegravir (study patients). The control group will be constituted by subjects who never received raltegravir, matched (in a ratio 1:3) with the study subjects by gender, age (± 3 years), CD4+ cells counts (± 50 cells) and HCV co-infection status yes/no). For control patients, the last antiretroviral regimen prescribed will be considered.