Degenerative diseases such as arteriosclerosis, vascular hypertension, cancer, arthritis, diabetes mellitus and other metabolic disorders, chronic infections and degenerative kidney and liver diseases have become the major challenge to American medicine because these diseases interfere so greatly with health and self sufficiency of people between the ages of 40 and 60 yrs. Optimal nutrition may play a direct role in controlling these diseases if the concept of genetotrophism has any validity. Adequate nutrition in all nutrients clearly plays an indirect role in decreasing the incidence of these diseases and in rehabilitating people who already suffer from them. These relationships are discussed particularly in regard to prevention, control, rehabilitation and need for research. The relationship of obesity to diabetes mellitus, hypertension and arthritis and of excessive leanness to chronic lung diseases is discussed. Subclinical vitamin deficiency disease may have adverse effects, sometimes delayed in appearance, upon gum structure, upon oral and gastric mucous membrane, upon hematopoietic organs and upon peripheral nerves. Adequate protein and vitamin intake often may prevent the progression of acute hepatitis into chronic liver disease. Adequate nutrition is a major factor in rehabilitation of persons with most chronic diseases. Methods applicable to public health programs are discussed. Much more research is necessary both at the public health level regarding incidence of chronic disease in obese or malnourished persons and at the basic level concerning factors which control growth and maintenance of cells and tissues. Eventually, aging should not be synonymous with disease and degeneration.