Chapter 6 focuses on relationships in Congress, examining why some members are more likely to work together than others. As collaboration is an inherently relational activity that requires agreement between two or more actors, social network analysis is used to account for the interdependence of members. This chapter demonstrates that the relationships among members of Congress are a function of strategic considerations, personal relationships, and shared policy goals. Most notably, almost half of the relationships in the collaborative Congress are bipartisan, as members expect that working across the aisle will broaden the appeal of a policy and significantly increase the likelihood it will be successful. Even in a polarized environment, members are clearly motivated to try and find common ground with members of the opposite party. Members are also more likely to collaborate when they have mutual friends, are from the same state, or sit on the same committee, reflecting how the existing interpersonal and institutional relationships in Congress can lower the costs of collaboration.