Data from two Phase IIb trials, POWER 1 and 2 (TMC114-C213 and C202), were pooled to examine the effect of baseline viral susceptibility on response to control protease inhibitors [CPI(s)] compared with response to darunavir (TMC114) given with low-dose ritonavir (darunavir/r) in treatment-experienced HIV patients. POWER 1 and 2 were randomized, controlled Phase IIb trials with a similar design. Patients with one or more primary PI mutations and HIV-1 RNA >1000 copies/ml were randomized to receive an optimized background regimen plus darunavir/r or CPI(s). POWER 1 and 2 week 24 efficacy (intent-to-treat using time-to-loss of virologic response algorithm) data were pooled and analyzed according to baseline subgroups of susceptibility to the CPI regimen, fold-change (FC) in EC(50) to darunavir, and number of darunavir resistance-associated mutations (RAMs). In total, 131 patients received darunavir/r 600/100 mg twice daily; 124 received CPI(s) [lopinavir/r, 20%; saquinavir/r, 19%; (fos)-amprenavir/r, 24%; atazanavir/r, 11%; and 23% used dual-boosted CPI(s)]. At baseline, 72% of patients were resistant (defined as FC) to their investigator-selected CPIs. At week 24, darunavir/r 600/100 mg twice daily provided greater efficacy benefits over CPI(s), even when the virus was predicted to be fully susceptible to the CPI. The response to darunavir decreased when FC to darunavir at baseline was >40 or when three or more darunavir RAMs (in addition to other PI mutations) were present at baseline. Darunavir/r 600/100 mg twice daily showed efficacy benefits over CPI use regardless of viral susceptibility at baseline, FC to darunavir or boosting type in a population of treatment-experienced HIV-infected patients.