Sport has become a highly differentiated social phenomenon in recent years and over the past decades there has been a considerable increase in the social significance of sport. Changes in society, for example individualization, or the growing significance of the health and body culture, or changing values, are consid-ered to be generative mechanisms for increasing social importance and the differen-tiation of modern sport. As a consequence, the classic model of traditional competi-tive sport is being supplemented by individualistic and hedonistic sport forms. Al-though discussions in sport sociology attribute the changes observed in recent dec-ades of sport participation to a socially determined differentiation of sport, this prem-ise has hardly ever been empirically tested. The present study examines to what ex-tent the postulated developments in sport can be observed on a micro level of those engaging in sport, by examining sport behaviour from a contemporary historical per-spective. Based on a life-course approach to research, a total of 1,739 over-50-year-olds in Germany were asked about their sport participation in a retrospective longitu-dinal study. Results show that the increasing differentiation of sport can be docu-mented by the more diversified forms of individual sport careers. During a 30-year observation period the popularity of competitive sport decreased and the variety of ways in which sport was organized increased. A differentiated analysis based on ex-amining three birth cohorts showed that the reported change in sport participation can be attributed to age, cohort, and period effects. In addition, the present study ex-amines how specific events in contemporary history are reflected in individual sport careers. Sport careers in Chemnitz (Eastern Germany) and Braunschweig (Western Germany) differed before German reunification, and these differences have evened out after the political change and the process of transformation.