Fixed dose combination lopinavir/ritonavir (LPV/r) is a widespread used antiretroviral drug belonging to the class of protease inhibitors (PIs). PIs are associated with an increased risk of myocardial infarction. However, data is available suggesting increased levels of plasma lipids are not the sole explanation for this observation. Treatment with LPV/r might lead to a decrease of endothelial function as well, thus explaining the increased risk of myocardial infarction besides increased plasma lipids. Raltegravir is a registered antiretroviral drug with no known cardiovascular side effects. We hypothesize that switching LPV/r to raltegravir in HIV-infected patients with suppressed plasma viral load (<50 copies/ml) will lead to an improvement of endothelial function.