This study will enroll African Americans and Caucasians who have high blood pressure, as well as African Americans and Caucasians who have normal blood pressure. Potential participants will go through a screening process that involves a medical history review, questionnaires, and blood pressure monitoring. Eligible participants will then be admitted to the research clinic for a 2-night stay. Participants' nutrition history and body measurements will be obtained, and a catheter will be inserted into the arm so that blood can be easily collected during the clinic stay. During the night, participants' breathing habits and movements will be monitored while they sleep. During the day, blood pressure and heart activity will be monitored frequently, including when participants are asked to perform mildly stressful tasks, such as giving a short speech. Various medications that affect heart rate and blood pressure will be given at different times during the study, and researchers will monitor participants' reactions to each medication. Lastly, participants will also complete psychological questionnaires.