In sports demography, demographic models, tools and concepts are applied to sporting populations. An approach based on the sociology of sport is also applied for the theoretical framework which defines the concept of “sporting career”. The first sports demography studies revealed the exceptional mobility of sports populations, the effects of age and sex, and the existence of invidivuals who drop their sporting activity but return to it later. While anchored in a longitudinal perspective, duration analysis, applied here to members of the French swimming federation between 1997 and 2003, sheds light on the timing of events in individuals’ sporting careers (beginning, end, club changes, temporary breaks), but also provides a means to assess the effect of these events on careers and on the duration of federation membership. Along each sporting career, the pattern of such events varies over time as the process of socialization advances.