The effective reduction of medical errors depends on an environment of safety for patients in both clinically-based and systems-oriented arenas. Formal teamwork training is proposed as a systems approach that will achieve these ends. In a study conducted by Dynamics Research Corporation, weaknesses and error patterns in Emergency Department teamwork were assessed, and a prospective evaluation of a formal teamwork training intervention was conducted. Improvements were obtained in five key teamwork measures, and most importantly, clinical errors were significantly reduced.