We describe the emergence of the proV47A mutation in three out of five HIV-2-infected individuals failing lopinavir/ritonavir-based HAART. The appearance of such mutated variants resulted in high levels of phenotypic resistance to lopinavir, cross-resistance to indinavir, amprenavir, and hypersusceptibility to saquinavir. A search in HIV-2 databases revealed that proV47A is present in 8.6% of protease inhibitor (PI)-experienced patients but absent in all PI-naive patients. Its selection may be a common mutational pathway for developing resistance to lopinavir/ritonavir in HIV-2.