A central claim in Robert Putnam’s theory of social capital is that participation in voluntary organizations can foster social trust among members that are active and engaged. Based on this claim, this article examines how duration of membership and member participation impacts upon levels of social trust among sports club members. The results show that neither participation nor duration impacts on levels of social trust – a result found in survey studies conducted in Denmark and the Netherlands. Sophisticated participation measures and the inclusion of duration of membership set this study apart from previous studies on social capital. The fact that no correlation can be identified between participation and duration on one side and social trust on the other adds weight to the claim that, even though numerous studies find higher levels of social trust among members of voluntary organizations than among non-members, this cannot be attributed to member socialization.