Emergency medical care is delivered by highly trained and motivated individuals working in groups. In some cases, these groups function as teams, but their teamwork has been poorly studied and rarely is the result of focused training. Medical outcome traditionally is described using patient parameters and often is related to the economics of care delivery. Errors in medical care typically are blamed on individuals and occasionally on system problems. Teams and teamwork, although a major part of the medical delivery system, usually are not included in training, outcome measures, or rigorous quality improvement efforts. This article outlines issues involved in the analysis of medical errors as they relate to measures of individual and team performance and introduces concepts related to emergency care teamwork and team training. Through analogy with aviation analysis of errors and corrective training medical care similarly is being analyzed and error-reduction efforts studied and implemented. The potential benefit of teamwork training for EMS personnel, including air medical crews, is discussed.