To determine the effectiveness of systematic, sustained, antihypertensive therapy in reducing morbidity and mortality from hypertension in a wide spectrum of persons with elevated blood pressure in 14 communities. During its course, the trial also obtained a direct measure of the prevalence, severity, and treatment status of representative white and black populations with high blood pressure in these 14 communities, and obtained an estimate of the extent of attainable reduction of complications of high blood pressure by an organized screening and blood pressure management program.