The study was carried out by four clinical and two resource centers (a Coordinating Center and a Nutrition and Educational Resource Center). It was to be Phase l of a long-term intervention trial to determine whether development of hypertension could be prevented in a population at special risk. The initial phase of the study was directed towards testing the feasibility of the intervention, alternative modes of recruitment, quantification of sodium and potassium intake, trends in blood pressure, and the pre-testing of various study procedures.