In the control group, patients will be allowed to change therapy for virological, toxicological or personal reasons. All variation will be recorded. Patients changing therapy will be still included in the ITT analysis, but will be considered failures in the AT analysis. Patients stopping therapy, for any reason and not resuming it within 3 months will be considered as failures for both the ITT and AT analysis In the STI arm, patients will stay off therapy until their CD4 count drop < 350 cells/mcL (one measurement will be considered sufficient). At that time point patients will resume the HAART regimen they were assuming before the STI period and will continue HAART until their CD4 count raises > 600 cells/mcL and their plasma HIV-RNA drops below the detection limit of 50 copies/ml (one measurement will be considered sufficient). When both the CD4 count and the viral load will be within these pre-set values they will stop therapy again. There is no limit to the number of interruptions and re-start cycles during the study period 160 patients will be allocated in the STI arm and 80 patients in the control arm.