Determination of clinical, lipid, and non-lipid risk factors has been the traditional approach for gauging an individual's risk for coronary artery disease (CAD). However, the IMT test, which uses sound waves to measure the thickness of the carotid artery, has been found to diagnose CAD and predict a person's risk for heart disease as well as or better than lipid and non-lipid risk factors. This study will use the IMT test to see if anti-HIV treatment and HIV infection affect a patient's risk of developing atherosclerosis (hardening of the arteries) by comparing carotid artery thickness among HIV infected adults taking PIs, HIV infected adults not taking PIs, and HIV uninfected adults.

There are 3 groups in this study. Group 1 will comprise HIV infected participants currently taking a PI-containing regimen. Group 2 will comprise HIV infected participants who are not taking PIs. Group 3 will comprise HIV uninfected participants. At each site, participants will be enrolled by "triads" consisting of an individual from each group. Each member of the triad will be closely matched by gender, age, smoking and menopausal status, race, and normal or hypertensive blood pressure. All 3 members of the triad must be identified before participants are registered to the study.

All participants will visit the clinic at Weeks 1, 24, 48, 72, 96, and 144 (3 years). At each visit, participants will have a physical exam, medical history and waist/hip ratio assessment, blood collection, and an IMT test. The absolute value for carotid IMT will be compared among the 3 groups. Viral load and CD4 counts will also be measured in Group 1 and 2 participants.