As the direct result of improved health measures and medical/dental care during the 20th century, the longevity of individuals within the United States has significantly lengthened from 45 years in 1900 to 75 years in the 1980s. It is now projected that during the remaining 2 decades of the 20th century, approximately 18% of the total American population will be 65 years and older by the year 2000. Paradoxically, success in reducing acute diseases and postponing death has resulted in costly long-term disabilities and complexities of chronic disease. This review focuses, therefore, on the major issues of prevention of chronic diseases to demonstrate that biologic aging is a normal sequela of developmental biology and not a disease; diseases are separated from aging. Emphasis is placed on advances in genetics, molecular biology, immunology, and neurology toward understanding the ultimate prevention of chronic disease. An emphasis on prevention during the development of the individual, from conception through senescence, is necessary.