The MedTeams project is a translational research effort to apply crew resource management (CRM) behavioral principles developed in aviation to emergency medical care. Hospital emergency departments share many of the same characteristics with workplaces where CRM is effective, such as time-stress, dispersed and complex information, multiple players, and high-stakes outcomes. Preliminary observations in emergency departments (ED) established that the same CRM behaviors employed by highly effective aviation teams could be useful in the ED (Weiner, Kanki, and Helmreich 1993; Simon, Morey, and Locke 1997). A retrospective review of ED closed claims revealed that failure to engage in one or more of these teamwork behaviors was associated with an adverse event and indemnity payments. In 43 percent of the cases reviewed, teamwork behaviors would have prevented or mitigated the adverse event had they been applied (Risser, Rice et al. 1999). Similar analyses attribute about 80 percent of anesthesia mishaps to human error and 70 percent of commercial aviation accidents to crew errors (Gardner-Bonneau 1993; Taggart 1994). Crew training has led to reductions in aviation mishaps beyond those produced by improvements in equipment and technology. The aviation community began introducing CRM training two decades ago and it is now required for all military and commercial U.S. aviation crews and air carriers operating internationally (Helmreich and Foushee 1993; Helmreich 1997). The basic principle of CRM is that crew communication and coordination behaviors are identifiable, teachable, and applicable to high-stakes environments. An additional principle is that those behaviors, although seen spontaneously, are not practiced reliably, regularly, or well unless specific training and reinforcement has established them. Specific CRM behaviors have been identified through experimentation and observation of high-reliability teams in demanding, time-stressed environments such as combat aviation and naval command and control centers (Leedom and Simon 1995; McIntyre and Salas 1995). Crew resource management training has been shown to be effective in these environments and is being extended into other domains (Helmreich and Foushee 1993; Salas et al. 1999). Finally, an essential principle of CRM is that a team needs to be formally established for teamwork behaviors to be effective. In contrast to the notion of a team as any loosely coordinated group of caregivers and support staff, the formal teamwork structure of this study stipulates that a team be made up of between 3 to 10 members. A team is composed of physicians, nurses, and technicians who are organized for a shift. The number of designated teams for a shift depends on factors such as staffing levels and patient volume. From these larger teams, ad hoc teams are formed to respond to emergent events such as resuscitations. In this model, teamwork is sustained by a shared set of teamwork skills rather than permanent assignments that carry over from day to day. Teamwork theory development has focused on input variables affecting team functioning such as task, work environment, and team member characteristics (Salas et al. 1992), what and how to train (Salas and Cannon-Bowers 2001), and outcome constructs of teamwork effectiveness (McIntyre, Salas 1995). Explanatory mechanisms of team processes exist in the form of constructs such as situational awareness and shared mental models, but relating team processes to work productivity outcomes has been limited by measurement difficulties with these constructs. Because this study examined the applicability of CRM to health care, a goal of this study was to generate a set of testable teamwork process–outcome propositions for future healthcare research. With respect to the training intervention, we sought to gain insight into the effectiveness of the training materials and methods, and features of the curriculum that needed revision. In addition, we sought to determine if the training intervention changed staff attitudes and behaviors and had an impact on patient care. These complementary perspectives are referred to as formative and summative evaluation in the education research literature (Bloom, Hastings, and Madaus 1971). The first objective of this study was to adapt an aviation-oriented teamwork curriculum to the particular circumstances of EDs by developing and then implementing a training curriculum (Emergency Team Coordination Course [ETCC]) organized around five team dimensions (maintain team structure and climate, apply problem-solving strategies, communicate with the team, execute plans and manage workload, and improve team skills) (Risser, Rice et al. 1999; Risser, Simon et al. 1999). The second objective was to evaluate the effectiveness of the intervention with measures developed to address three outcome constructs: Team Behaviors, Attitudes and Opinions, and ED Performance.