Actualit: Physical activity is very important for the harmonious development of the body of adolescents. Most of the time schoolchildren spend at school and requires a predominantly static position during study. Lack of physical activity in adolescents seems to be an urgent problem, since it causes significant damage to the health of students and requires correction. Purpose: to analyze the research data on the influence of physical activity on the physical development of adolescents. Materials and methods: The author studied the results of works devoted to the anatomical and physiological features of the physical development of adolescents at the age of 12-15 years, as well as the influence of the level of physical activity on the harmony of physical development and the somatotype of students. The data of a long-term study were analyzed, in which the influence of different sports (swimming, rowing, shooting) on anthropometric and morphological changes in the body of adolescents aged 11-17 years was studied. In addition, the influence of physical activity on the level of general working capacity of schoolchildren at the age of 11-17 was studied. Results: As a result of the study, it was found that schoolchildren at the age of 12-15 are generally characterized by harmonious physical development. In this case, three somatotypes are distinguished: meso-, macro- and microsomatotypes. It has been shown that purposeful physical activity has a more pronounced effect on the physical condition of adolescents of both sexes at the age of 11-17 years. It has also been proven that physical activity is reflected in a significant improvement in cardiovascular and respiratory function. Swimming has the most pronounced effect on the hemodynamic parameters of adolescents. It was also shown that schoolchildren who go in for sports have high physical performance and stabilization of functional indicators after the end of physical activity. Conclusions: In general, purposeful and systematic physical activity has a pronounced positive effect on the physical development of adolescents. The materials of this article can be useful for specialists dealing with the correction of the physical development of schoolchildren in conditions of insufficient physical activity, as well as the development of special programs for sports sections.