Since June 2007, raltegravir has been available in Switzerland within a named patient program for patients who have virologic failure, triple class experience and resistance, and no other treatment options. This proposal has been designed to evaluate efficacy and safety data among patients who receive raltegravir within the routine clinical practice in Switzerland and who participate in the Swiss HIV Cohort Study. This is a combined retrospective analysis of patients who already received raltegravir and a prospective part of patients who enter the named patient program and will be followed up in a standardized way. In the prospective part, patients will also be able to receive raltegravir in case of intolerance to their current medication with virologic suppression.