Membership in voluntary associations is often assumed to have a homogenizing or diversifying impact on the social composition of members' personal relations. In this study, we examine these assertions empirically in a sample (n = 818) comprising active members of voluntary associations in a typical midsized Swedish community. We investigate whether people whom active members of voluntary associations have met through their voluntary activities are more or less likely to share their social characteristics than people whom they have met elsewhere. Our results show that acquaintances whom our respondents have acquired within voluntary associations are less likely to share several of their significant social characteristics than other members of their personal networks, but more likely to reside in their vicinity than others. Consequently, our results give fairly robust support to the “integrating hypothesis” according to which voluntary associations contribute to the social diversification of their members' personal networks. We do, however, emphasize the principally important aspects of our results, according to which relations acquired through involvement in voluntary associations may have simultaneously homogenizing and diversifying effects on individuals' personal networks. Furthermore, the effect may also depend on the specific dimension(s) of the networks under consideration.