3 | 75 When do young adults stop practising a sport? in fitness, bicycling and swimming). Hence it should come as no surprise that there is overlap between the concepts and determinants of sport participation and of leisure time physical activity (Coakley, 2004). Although physical activity and sport participation are to some extent related, little is known about stopping sport participation from a life-event perspective (Li et al., 2009). Generally, sport participation research has focused on differences between age groups and sometimes on people with different household compositions and employment statuses. Little attention has been paid to the dynamic of when exactly people drop out of sport. Reliance on cross-sectional surveys has generally hindered the drawing of conclusions in terms of causes and effects (Kraaykamp et al., 2013; Lunn, 2010). It has been suggested that studying the impact of life events on dropping out of a sport or sport club in young adulthood could help overcome some of the current limitations in explaining sport participation (Hirvensalo and Lintunen, 2011) This article does just that. We use a dynamic design to investigate how life events in young adulthood influence engagement in sport. Our main research question is: to what extent are stopping a sport and ending a sport clubmembership affected by major life events among young adults? We focus on beginning to work, starting to live on one’s own, starting to cohabit or getting married, and the birth of one’s first child. These life events are specifically chosen because they are commonly experienced within the life phase under investigation, and they represent major transitions in the process of becoming an adult in the life domains of employment, residency, personal relationships and parenting (Arnett, 2007; Kilmartin, 2000; Zarrett & Eccles, 2006). Because of the social significance of sport clubs within European societies (Breuer, Hoekman, Nagel, & Werff, 2015; Janssens & Verweel, 2014), we look not only at stopping participation in a sport in general, but also at ending a sport club membership in particular. The current study advances earlier research in several ways: by employing a life-course approach (Engel & Nagel, 2011), by analysing four major life events in different life domains, by employing detailed retrospective data and event history techniques, and by developing a theoretical framework for explaining the effects of major life events on the risks to stop practising a sport and end a sport club membership. Our framework highlights changes in temporal and social resources associated with the occurrence of these life events and their consequences for the risk of stopping sport participation (Kraaykamp