The purpose of this paper then is to demonstrate that teamwork is an important component of HROs. While moving health care toward team-based work will not automatically result in high reliability, there are many parallels between teams and HROs (Knox and Simpson 2004; Wilson et al. 2005). To justify our argument, we begin by providing an overview of teams, teamwork, and strategies for promoting team effectiveness. Much has been written about these topics in domains where high reliability is critical because the consequences of error are great (e.g., the military, commercial aviation, and air traffic control) (Salas and Cannon-Bowers 2000; Davies 2001; Baker et al. 2003; Salas Sims and Kleien 2004). Later in this document, we describe the key characteristics of HROs. The concept of HROs has been around for more than 20 years, but has only recently begun to take hold in health care with the publication of To Err Is Human and AHRQ's patient safety agenda. In this section, we compare the fundamental features of teamwork and the critical characteristics of HROs and demonstrate how these characteristics are interwoven as well as how and why the HRO environment demands teamwork. Finally, although the science of teamwork has been around for over 30 years, it is only recently that this concept has begun to take hold in health care. In the last section we present a series of challenges researchers and practitioners need to address to advance the health care community's understanding of team performance and instantiate these practices as part of health care's quest to achieved high reliability.