Ischemic cardiovascular disease and hypertension occur in persons with HIV infection, and the incidence and prevalence may increase over time as the infected population ages. Standard pharmacologic interventions for these illnesses often include calcium channel blockers (CCBs). Many of the calcium channel blockers are metabolized by cytochrome P450 3A4 (CYP 3A4), which is inhibited by some protease inhibitors (PIs). Thus, there is potential for clinically significant interactions between CCBs and PIs. The presence of significant drug-drug interactions may influence the dosing, monitoring, and choosing of CCBs and/or PIs when used in persons with HIV infection. Because of the potential concomitant use of CCBs with the PI combination IDV/RTV, this study will evaluate bi-directional drug-drug interactions between 2 commonly used CCBs and IDV/RTV. This information should assist clinicians in choosing the appropriate CCBs to treat hypertension or cardiovascular disease in persons taking PIs.