This will be a retrospective analysis of efficacy, safety and tolerability of raltegravir as part of an optimized therapy in a clinical setting.

Follow-up is calculated from the treatment initiation (with or without raltegravir) up to the date of discontinuation of the considered regimen or the date of last visit or the date of lost to follow-up, whichever came first.

The Aim of the study is to evaluate the efficacy and safety of raltegravir-containing regimens in a urban clinic setting.

Inclusion Criteria:

• Subjects who received raltegravir and were previously exposed to NRTIs, NNRTIs, PIs, regardless of the stage of HIV disease at the start of the treatment.

Exclusion Criteria:

• None

This study will include subjects who received raltegravir and were previously exposed to NRTIs, NNRTIs, PIs, regardless of the stage of HIV disease at the start of the treatment.

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.