HIV-1 protease inhibitors often cause dyslipidemia, necessitating the use of lipid-lowering agents such as rosuvastatin. However, when given concomitantly, these therapeutic agents often exhibit adverse drug interactions. In this study (phase I open-label trial, n = 12 HIV-1 seronegative participants), the authors assessed the drug interactions between darunavir/ritonavir given in combination with rosuvastatin. Participants were randomized to receive rosuvastatin (10 mg/day) or darunavir/ritonavir (600/100 mg twice daily) alone for 7 days in a crossover design followed by combination therapy for 7 days with intervening 7-day washout periods. Intensive blood sampling for pharmacokinetics and fasting lipids was performed on days 7, 21, and 35. The geometric mean AUC(0-24 h) of rosuvastatin increased from 109 to 161 ng·h/mL (P < .005) and C(max) increased 6.7 to 16.3 ng/mL (P < .001) when coadministered with darunavir/ritonavir. In the presence of darunavir/ritonavir and rosuvastatin, total cholesterol and triglyceride levels increased by 10% (P = .007) and 56% (P = .011), whereas the high-density lipoprotein cholesterol levels decreased by 13% (P = .006) relative to rosuvastatin administration alone. There were no significant adverse events attributable to the coadministration of these drugs. Rosuvastatin levels increase in the presence of darunavir/ritonavir coadministration, whereas the lipid-lowering benefits are blunted. The clinical significance of these changes requires further investigation.