This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Primary Objectives: 1. to evaluate the short term safety tolerability of raltegravir added to an initial stable background therapy in HIV-1 2. to evaluate the steady state plasma concentration profiles and pharmacokinetic parameters of raltgravir added to the stable background therapy 3. to evaluate the safety and tolerability of raltegravir at the selkected dose in combination with optimized background therapy