This chapter summarizes the research literature on team effectiveness, highlighting findings on the key features that create challenges for team science outlined in Chapter 1. Based on its review of the literature (e.g., Kozlowski and Ilgen, 2006; Marks, Mathieu, and Zaccaro, 2001; Salas, Goodwin, and Burke, 2009), the committee defines team effectiveness as follows: Team effectiveness, also referred to as team performance, is a team's capacity to achieve its goals and objectives. This capacity to achieve goals and objectives leads to improved outcomes for the team members (e.g., team member satisfaction and willingness to remain together) as well as outcomes produced or influenced by the team. In a science team or larger group, the outcomes include new research findings or methods and may also include translational applications of the research.