This volume examines the ongoing, worldwide epidemiological transition in which acute infectious diseases are being superseded by chronic diseases as the predominant causes of morbidity and mortality; age at death has shifted from childhood to older adult ages; and life expectancy, population, and the proportion of older people are increasing. This transition constitutes a fundamental change in the human condition, and an understanding of the historical process behind it is thus of major importance. This study is the first to document the transition in a single country, drawing on records of cause-specific mortality since the eighteenth century in England, with comparative data from other Western countries. Alexander Mercer discusses possible causes of specific disease trends, reassessing the relative importance of "health interventions" and "standard of living" as determinants of increased life expectancy, and presents a new theory of how chronic diseases have developed. As specific microorganisms have been established as causal agents in chronic diseases that account for a significant proportion of "premature" deaths, the study suggests that a new conceptualization of the epidemiological transition is required, one that takes into account interrelationships between infectious diseases, between infections and chronic diseases, and between disorders underlying different chronic diseases. Alexander Mercer is an independent researcher and the author of Disease, Mortality and Population in Transition: Epidemiological-Demographic Change in England Since the EighteenthCentury as Part of a Global Phenomenon.