Low-dose ritonavir substantially enhances lopinavir plasma levels, and lopinavir/ritonavir (LPV/r) is effective as part of a combination therapy in both naive and PI-experienced patients. Furthermore, lopinavir is known to have a high genetic barrier to selection of resistance. LPV/r monotherapy could thus have the right combination of potency, favorable pharmacokinetics, and high genetic barrier needed to suppress viral replication and prevent the selection of lopinavir resistance. Preliminary results with "maintenance"LPV/r monotherapy show interesting results but data from randomized studies are needed.