High blood pressure is a serious health problem. In terms of diet recommendations, people with this condition are encouraged to eat a low sodium and high potassium diet. It is believed that genetics may play a role in the development of high blood pressure and may affect changes in blood pressure levels, including changes brought on by sodium and potassium. This study will identify genetic factors that may influence blood pressure changes due to increased salt or potassium intake in people with mildly elevated blood pressure and in their family members.