The article by Abdel R. Omran introduces the concept of the Epidemiologic Transition, a theory that integrates demographic, biologic, sociologic, economic, and psychologic factors to explain population dynamics. The theory focuses on the complex changes in health and disease patterns and their interactions with demographic, economic, and sociologic determinants. Omran emphasizes that mortality is a fundamental factor in population dynamics, and the Epidemiologic Transition is characterized by a shift from high mortality and morbidity due to infectious diseases to lower mortality and morbidity due to degenerative and man-made diseases. This transition is divided into three stages: the Age of Pestilence and Famine, the Age of Receding Pandemics, and the Age of Degenerative and Man-Made Diseases. The article also discusses the relative risks of mortality by age and sex, the interactions between demographic and socioeconomic transitions, and the economic implications of the transition. Three basic models of the Epidemiologic Transition are presented: the classical or western model, the accelerated model, and the contemporary or delayed model. The article concludes by highlighting the importance of understanding these transitions for population policy-making and addressing the challenges associated with disequilibrating population movements.The article by Abdel R. Omran introduces the concept of the Epidemiologic Transition, a theory that integrates demographic, biologic, sociologic, economic, and psychologic factors to explain population dynamics. The theory focuses on the complex changes in health and disease patterns and their interactions with demographic, economic, and sociologic determinants. Omran emphasizes that mortality is a fundamental factor in population dynamics, and the Epidemiologic Transition is characterized by a shift from high mortality and morbidity due to infectious diseases to lower mortality and morbidity due to degenerative and man-made diseases. This transition is divided into three stages: the Age of Pestilence and Famine, the Age of Receding Pandemics, and the Age of Degenerative and Man-Made Diseases. The article also discusses the relative risks of mortality by age and sex, the interactions between demographic and socioeconomic transitions, and the economic implications of the transition. Three basic models of the Epidemiologic Transition are presented: the classical or western model, the accelerated model, and the contemporary or delayed model. The article concludes by highlighting the importance of understanding these transitions for population policy-making and addressing the challenges associated with disequilibrating population movements.