This is a multi-center, open-label (doctors and patients know which drug is being administered), Phase IIIb clinical trial to evaluate differences in effectiveness, safety, and tolerability of darunavir/ritonavir by sex and/or race over a 48-week treatment period. This study will be conducted in HIV positive women and men who have been treated previously with antiretroviral therapy. This study will enroll 70% women and will be conducted in the U.S., Puerto Rico, Mexico and Canada in approximately 420 patients who will receive darunavir 600 mg and ritonavir 100 mg twice daily. The primary objective of this study is to determine the percentage of patients who achieve virologic response, defined as a viral load (VL) of <50 copies/mL at week 48. Secondary study objectives include comparisons of endpoints between women and men as well as race across multiple parameters including but not limited to change in CD4 count from baseline to week 48, time to loss of virologic response (TLOVR), changes in metabolic parameters (blood chemistry), etc.