Purpose. The aim of the study was to determine the influence of environmental factors on the physical development of girls and boys at puberty. Basic procedure. The sample of adolescents of both sexes was studied using comprehensive measuring data and information from surveys. To examine correlations between quantitative and qualitative data the factor analysis was used (onedimensional test F for every variable). Main findings. The biological indices of social stratification of adolescents under study were the results of medicine ball throw test and maximal anaerobic power (MAP). The MAP was calculated using results of the standing broad jump test. The highest level of physical development was noted among the group of students with the best environmental conditions. The majority of subjects with a high level of physical development came from families with a single child and with monthly net income per person from 301 to 500 PLN and more. Their parents had at least a secondary education and were either white-collar or blue-collar workers. Conclusions. To enhance physical fitness of young people the pre-pubescence period should be used better. During the pubescence period children should have every opportunity to take part in various extra curricular classes during the school year. In addition, appropriate conditions for active leisure pursuits (during summer or winter holidays) should be created for children to develop their physical recreation interests.