Significance. Population growth and aging pose serious social, economic, and political challenges worldwide. This highlights the need for a thorough analysis of various theories, trends, factors, and consequences affecting demographic structure. Demographic and epidemiological transitions are fundamental concepts that help explain these phenomena. Understanding and analyzing these concepts is crucial for health planning, organization, and creating flexible health systems that can respond to changing needs. The purpose of the study. The purpose of this work is to systematize information on leading modern demographic theories that explain population dynamics and structure at the global and regional levels. Material and methods. А bibliometric analysis of contemporary medical foreign and domestic literature relevant to the subject under investigation. Results. The main theoretical works by scientists who have made significant contributions to the understanding and development of the concepts of demographic and epidemiological transitions have been analyzed and described. It has been noted that there are many concepts of demographic transitions (second, third, etc.), which represent different scenarios for demographic development in individual countries, regions, or the world. The first demographic transition emphasizes fertility and mortality. The second demographic transition highlights social changes in families in Western Europe. The third demographic transition presents a pessimistic scenario affecting the composition of populations associated with migration policies of host countries. The fourth demographic transition considers migration as a positive factor, but it can have negative consequences if its essence and corresponding migration policies are misunderstood. With regard to the epidemiological transition and its impact on mortality and life expectancy, this paper describes the main factors, periods, and models that describe the essence of this theory. Discussion. At the moment, the world's population is going through different stages of demographic and epidemiological transitions. According to some experts, Russia has started the second demographic transition and is just beginning this process. Regarding the epidemiological transition, there are several factors that influence mortality rates and life expectancies, as well as models and concepts that describe the theory. However, according to other experts, there is still no clear answer as to whether the Russian Federation is in a specific stage of the epidemiological transition or not. Conclusions. Understanding these concepts is crucial for developing effective policy measures to address the challenges associated with population growth and aging, as it allows for predicting future demographic trends and making informed decisions regarding the development of healthcare, social protection, and other sectors that contribute to society's well-being. In particular, this is significant in the context of the Russian Federation's current trend towards an increasing proportion of older age groups and slowing population growth. The results of this study can be applied by researchers in public health and by public authorities responsible for developing policies in health and social areas.