In OECD (Organization for Economic Cooperation and Development) countries (Australia, Austria, Belgium, Canada, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Japan, Luxembourg, Netherlands, New Zealand, Norway, Portugal, Spain, Sweden, Switzerland, United Kingdom, and United States), mortality at ages 35-69 y has fallen by 38% since 1955 and the risk of dying before age 70 y has been reduced to 23%. In middle and old age, chronic and degenerative diseases are the principal causes of death. Neoplasms, ischemic heart disease, and cerebrovascular disease cause three-quarters of all deaths at 35-69 y of age and two-thirds at older ages. Mortality from vascular disease has declined rapidly. Mortality from neoplasms has not declined rapidly; however, mortality not attributed to smoking has and there is no general increase in cancer attributable to industrial development. Despite lower death rates in nonsmokers than in cigarette smokers, vascular disease and neoplasms remain the targets for prevention. With increased duration of life, conditions that cause serious disability in old age become more important and the principal foci for research. These conditions are also chronic and degenerative.