In the current investigation, we studied sex differences in belonging needs by exploring men's and women's attachment to groups. Previous work has shown that women's social needs tend to be expressed in terms of relational bonds, whereas men's also have a strong collective component (e.g. Gabriel & Gardner, 1999). In this research, we asked men and women to consider one of their important group memberships and to complete Prentice, Miller, and Lightdale's (1994) group attachment scales. In two studies, findings showed that the extent to which a woman was relationally attached (i.e. felt close to the other members of her group) was sufficient to explain the group's importance to her. In contrast, men's ratings of group importance depended upon the extent of both relational and collective attachment (i.e. attached to the group identity). Implications for real-world groups are discussed. DIFFERENCES in the way that men and women approach the social world tend to captivate and amuse us. A favorite topic of sit-coms and standup comics, a standard scenario might involve a skirmish between a wife who is completely fixated on the minutia of her social relationships and a husband who is oblivious and G P I R