The staff in trauma centers are faced with complex problems under time pressure. Despite the introduction of standard protocols, the diversity of injuries that can occur requires a coordinated approach to the evaluation and treatment for each patient. Trauma care involves complex teamwork under time pressure, and teamwork errors endanger patient care and increase costs. Our proposed ethnographic study will use observation and detailed analysis of video recordings of trauma resuscitations to determine the nature and extent of teamwork errors in a trauma center. This detailed study of complex teamwork will uncover the causes of teamwork errors in collaborative high-risk environments. Methods will be developed to understand how teams work and where difficulties arise. This work will yield detailed descriptions of errors and their causes, a taxonomy of teamwork errors, information on how to improve team performance, and guides to the use of technology for teamwork support. It extends the level of detail of ethnographic research so that we can achieve precision in the understanding of procedures which are difficult to monitor automatically but where step-by-step records are essential to detect the causes of errors. Understanding and improving the effectiveness of trauma teams has direct benefit to society. Further, complex collaborations are ubiquitous in modern enterprises and these results could improve collaborations both in terms of quality and productivity across organizations. In addition, this work will serve to develop the skills needed by a new cadre of researchers with knowledge of computer-supported collaborative work, video-content analysis and cooperative research.