The Framingham Heart Study included 1644 spouse pairs as part of the original cohort. The new Framingham Offspring Study consists of examination of the offspring of these matings. Over 5000 offspring and their spouses have been identified and invited to an examination at the Framingham Heart Study facilities. Approximately 82% of the offspring still live in the New England area. Response rates for those living in New England are currently about 80%. Due to vigorous efforts to contact offspring who have moved from New England, it is estimated that over 20% of this group will also be examined. Comparison of age-specific means for the original cohort in 1950 and the offspring in 1972 show apparent reductions in blood pressure, serum cholesterol, and cigarette smoking in the offspring. In contrast, height in men and women and relative weight in men show significant increases in the offspring. Methodologic differences may account for certain of these changes, but it is possible that the observed reduction in the major CHD risk factors may result from generally increased health awareness in this sample or the institution of primary prevention measures.