Human immunodeficiency virus-infected patients on antiretroviral drug therapy frequently experience hepatotoxicity, the underlying mechanism of which is poorly understood. Hepatotoxicity from other compounds such as bosentan and troglitazone has been attributed, in part, to inhibition of hepatocyte bile acid excretion. This work tested the hypothesis that antiretroviral drugs modulate hepatic bile acid transport. Ritonavir (28 M ϭ 2.1 and 6.4 M in human and rat, respectively), saquinavir (IC 50 ϭ 6.7 and 20 M, respectively), and efavirenz (IC 50 ϭ 43 and 97 M, respectively). Nevirapine (75 M) had no effect on bile acid transport in any model system. In conclusion, ritonavir, saquinavir, and efavirenz, but not nevirapine, inhibited both the hepatic uptake and biliary excretion of taurocholate.