The study lasted 24 weeks. Participants were randomly assigned to one of two arms. Participants in Arm A were administered raltegravir in addition to their usual ART regimen from study entry until Week 12. At Week 12, subjects halted raltegravir use and received a placebo until Week 24. Participants in Arm B were administered the placebo in addition to their usual ART regimen from study entry until Week 12. At Week 12, subjects halted the placebo and received raltegravir until Week 24. A real-time polymerase chain reaction (PCR) single copy assay (SCA) capable of detecting 1 copy of HIV RNA was used to assay viral load. The cross-over design allowed assessment of the effect of intensification with raltegravir between the two arms at Weeks 10/12 and every participant enrolled in the study receiving raltegravir for 12 weeks. Primary analysis focused on weeks 10/12 measurement and with no washout period, typical analysis of cross-over design was not intended.