Randomized, open-label, prospective clinical trial assessing efficacy and safety on hyperlipidemia of a switching from a regimen including one protease inhibitor and one thymidine analogue to atazanavir/ritonavir plus abacavir/lamivudine or tenofovir/emtricitabine. Adult HIV-infected patients on their first antiretroviral therapy (of at least 48-week duration), including one protease inhibitor and zidovudine or stavudine, with stable immunovirologic features, and having diagnosis of persisting hyperlipidemia, were randomized to replace current treatment with atazanavir/ritonavir plus abacavir/lamivudine (arm A) or tenofovir/emtricitabine (arm B), and were followed for 48 weeks. Eighty-nine patients were enrolled: 42 patients were randomized to arm A, and 47 to arm B. At the end of the 48-week follow-up, incidence of virologic failure was comparable in both arms, and associated with a poor drug compliance. Increase in CD4 lymphocyte count was significantly higher in arm A after a 24-week study period (62.5 versus 39.2 x 10(6) cells/L; p < 0.05), while immunologic responses were comparable at the end of 48-week follow-up (91.5 versus 83.6; p > 0.05). A statistically significant reduction (-15.4%) in mean triglyceridaemia versus respective baseline values was reported in both groups (p < 0.05), without statistically significant difference between arm A and B. Similar results were reported for total cholesterol and low-density lipoprotein (LDL) cholesterol levels. Safety and tolerability profiles were comparable in both groups. Switching from a protease inhibitor- and thymidine analogue-based antiretroviral regimen to atazanavir/ritonavir plus abacavir/lamivudine or tenofovir/emtricitabine proved effective in the management of hyperlipidemia, without significant differences in lipid-lowering effect, virologic efficacy, and safety profile between these regimens.