Despite all endeavours for activating different groups of the population sport is also today a domain of the youth. Persons at the age up to 20 among athletes are by far overrepresented in comparison to their share in the population. The sports club, at this age, does not only very far reduce to the background all other forms of organization of leisure time activities but forms far more the most popular type of participation in voluntary organizations. In contrast to many common ideas this fact holds true for all social groups. The quota of persons who at least once a month are engaged in extracurricular sports activities or who are organized in sport clubs, is at the age between 16 and 20 nearly as high in the lower classes as it is in the middle classes. Only after the 20th year of age the curves of participation in sports are diverging fairly well in the social groups, i.e. the members of lower social classes where obviously sport is considered as a typical behaviour of youth, are withdrawing from sport. The same holds true for the engagement in leisure time activities in general. The strong social differentiations in the level of participation in sports in general, in the type of the chosen sports discipline and leisure time activities and in the membership in voluntary organizations are fully implemented only with adults. Obviously, sport belongs to the elements of an independent youth culture in leisure time which also comprises the female members of lower classes, who at higher age are especially diverging from the activity samples of middle classes.