Each of the four clinical centers recruited 200 or more eligible 25 to 49 year old individuals (total 841), either identified through any of a number of multiple community sources, or through an index of hypertensive cases. The clinical investigators aided by statistical and data processing support from the Data Coordinating Center and intervention support through a special Nutrition and Education Resources Center, formed the collaborative group to test the working hypothesis. The study protocol was completed in the fall of 1982. Recruitment ended September 30, 1983. The three-year follow-up period ended August 1986. Analysis of the data ended in December 1988.