The analysis will primarily use descriptive statistics. In addition, we will assess the duration of virologic response and focus on predictors of HIV RNA suppression during a follow-up of at least 6 months. In the prospective part, we will assess trough plasma levels of raltegravir and other antiretrovirals. In patients who will develop virologic failure, genotypic and phenotypic resistance to raltegravir (and other antiretrovirals) will be performed to characterize the evolution of resistance during the raltegravir-containing regimen.