 In HIV-infected subjects who have virologically failed first-line antiretroviral therapy comprising 2NtRTI NNRTI a regimen of second-line therapy incorporating ritonavir-boosted lopinavir and raltegravir provides comparable i.e., non-inferior antiretroviral efficacy over 48 weeks to a regimen containing ritonavir-boosted lopinavir and 2-3NtRTIs. 