High blood pressure affects nearly one third of all individuals in the United States. It is especially common in African Americans, with more than 40% of African Americans diagnosed with this condition. High blood pressure usually develops earlier in life and is more severe in African Americans than in other racial or ethnic groups. Many factors can cause high blood pressure, including stress, diet, diabetes, kidney disease, or obesity. Previous studies have also shown that genetic variations on two regions of chromosomes 6 and 21 may predispose some people to develop high blood pressure. Admixture mapping is a type of genetic analysis that aims to identify disease-causing genetic variations across different populations of people. Using admixture mapping, this study will examine previously collected genetic samples from African American participants in the Family Blood Pressure Program (FBPP) study and from African American, Mexican American, Nigerian, and Jamaican participants enrolled in other clinical studies. Study researchers will analyze the samples to identify and characterize genetic variations that are associated with an increased risk of high blood pressure in the African American population, as well as other racial and ethnic groups.