"This paper examines the roles of cosmopolitans and locals in transnational teams that work on knowledge-intensive projects. I propose that cosmopolitan and local team members can help their teams to acquire and apply knowledge more effectively, by bringing both internal and external knowledge to their teams and enabling them to more successfully transform this knowledge into improved project performance. Findings from a study of 96 project teams at an international development agency reveal that the roles of cosmopolitans and locals were complex and sometimes valuable, but cosmopolitans offered greater benefits than locals and too many of each could hurt. Implications for theory and research on international management, virtual teams, exploration and exploitation, and organizational knowledge are discussed."