This paper considers the effects of health conditions in childhood on an individual's mortality risks as an adult. It examines epidemiologic evidence on some of the major mechanisms expected to create a linkage between childhood and adult mortality and reviews demographic and epidemiologic studies for evidence of the hypothesized linkages. The circumstances under which health conditions in childhood can be expected to influence adult mortality include disease processes associated with respiratory tuberculosis, hepatitis B and cirrhosis/liver cancer, rheumatic heart disease, and respiratory infections/bronchitis. Other potential mechanisms include persistent viruses, dietary practices, and the burden of infectious diseases in childhood. Many empirical studies support the notion that childhood conditions play a major role in adult mortality, but only in the case of respiratory tuberculosis has the demographic importance of a specific mechanism been established by cohort studies. One's date and place of birth also appear to be persistently associated with risks of adult death in a wide variety of circumstances. An individual's height, perhaps the single best indicator of nutritional and disease environment in childhood, has recently been linked to adult mortality, especially from cardiovascular diseases. Further research is needed, however, before causal mechanisms can be identified.