The gender dynamics of cross-sex friendships provide information about two fundamental aspects of all social relationships: solidarity and hierarchy. This article analyzes how gender stereotypes activated in cross-sex friendships produce interpretations of behavior that, in turn, affect the solidarity, hierarchy, and ultimate viability of cross-sex friendships. Given that females' behaviors are more likely to be interpreted in terms of gender stereotypes about women's prosociability, their behavior is less likely to produce hierarchy. In contrast, given that males' behaviors are more likely to be interpreted in terms of gender stereotypes about men's instrumentality, their behavior is more likely to produce hierarchy. Because hierarchy is an impediment to solidarity, the operation of gender stereotypes in cross-sex friendships builds into such relationships the potential for their demise. The role of the broader social context in lessening the destructive impact of gender stereotypes is discussed.