This is a randomized controlled pilot study to compare the safety and efficacy of substitution of atazanavir (ATV) or ATV/RTV for ritonavir boosted PI in patients with ongoing viremia who are experiencing hyperlipidemia and/or requiring treatment with lipid lowering agents. In this study 60 subjects on a ritonavir boosted PI-containing antiretroviral regimen who are experiencing hyperlipidemia and ongoing HIV viremia will be randomized in a 1:1:1 ratio to either switch the ritonavir boosted PI component of the antiretroviral regimen to ATV or ATV/RTV, or continue the ritonavir boosted PI-based regimen.