Raltegravir is the first integrase strand transfer inhibitor approved for the treatment of HIV-1 infection. As the first agent in this new class of antiretroviral therapies, raltegravir has demonstrated safety and efficacy in treatment-naive as well as heavily pretreated HIV-infected patients failing therapy with multidrug-resistant virus. Raltegravir has a favorable drug interaction profile that permits both administration to a wide, demographically diverse patient population and coadministration with many other therapeutic agents, including antiretroviral agents and supportive medications, without restrictions or dose adjustment. Data through 96 weeks of follow-up in three phase III studies, protocol 021 (STARTMRK) in treatment-naive patients, and protocols 018 (BENCHMRK-1) and 019 (BENCHMRK-2) in treatment-experienced patients, demonstrated the potent and durable antiretroviral and immunologic effects and the favorable long-term safety profile of raltegravir in both treatment-naive and treatment-experienced patients. Raltegravir represents an important addition to the current armamentarium for the treatment of HIV infection.