An ongoing study instituted in Framingham, Massachusetts in 1948. Framingham is a community thought to have a reasonably stable population which could be studied over a long time. Its design was to enroll a large number of persons, give them thorough physical, laboratory, and x-ray examinations every two years, as well as record their medical histories, throughout their lives. 5209 men and women between the ages of 30 and 62 years were enrolled. Numerous scientific papers have been written from the study, and a substantial amount of important information has been added to the field of medicine.