Pharmacologic boosting of protease inhibitors with ritonavir has become standard practice in antiretroviral therapy. Patients are instructed to take ritonavir at the same time as its accompanying protease inhibitor. However, ritonavir is unpopular with many patients because of its large size and because of the recommended need for refrigeration. This study will test the hypothesis that adherence to ritonavir is inferior to adherence to its accompanying protease inhibitor in patients receiving such therapy.