The study involves four field centers; a coordinating center; and five reading centers including an echocardiography reading center, an ultrasound reading center, a cerebral MRI reading center, and a retinal reading center; and a central blood analysis laboratory. Protocol development began in June, 1988, and recruitment for the first clinical examination began in June, 1989. Examination of 5,201 participants (2,962 women and 2,239 men) was completed in May, 1990. Two brief interim examinations were conducted during 1990-1992. A more extensive clinical examination in 1992-1993 was repeated to assess change in major subclinical disease; at that time, an additional cohort of 672 African Americans was recruited to improve minority representation and assessment of black-white differences. Since 1993, annual examinations have focused on a different major non-invasive measure each time, to reduce participant burden.