Life expectancies are increasing in populations throughout the world. As infectious diseases decline as causes of mortality, certain degenerative diseases including cardiovascular disease and cancer account for an increasing percentage of deaths. As more people survive into old age, the intrinsic limits on the human life span will be reached. It is clear that genetic factors have a strong influence on the life span. It is not clear, however, that there are identifiable longevous body types (morphotypes). For the first time in human history, large numbers of people 80 years old and older are available for study. If there is an association between body form and composition and superior longevity, it should be possible to identify its major aspects. Monitoring changes in body composition throughout the life cycle and the retention of reserves to be drawn upon when disease or trauma threaten life may provide the basis for prediction of the course of life threatening diseases. The unusually high survival of morphotypes classifiable as "moderately obese" casts doubt on standards recommending "ideal weights for height" if the criterion in question is survival.