Collaboration in complex and dynamic environments such as hospitals, airlines, and disaster response teams is challenging. High performance requires smooth coordination across multiple groups whose incentives, cultures, and routines can conflict. In this paper, we present an in-depth case study of a hospital's operating room practices to understand challenges associated with multiple group coordination and how information technology may help. We use the concept of trajectory to focus our observations and interviews on workflow across groups and critical events when coordination breaks down. A careful examination of the sources, coping mechanisms, and consequences of coordination breakdowns suggests three factors whose absence may impede effective responses to unexpected interruptions: (1) trajectory awareness of what is going on beyond a person's immediate workspace, (2) information systems integration, and (3) information pooling and learning at the organizational level. We conclude with technological recommendations to promote trajectory awareness and to automate information gathering and monitoring, so as to facilitate multiple group coordination in complex and dynamic task environments.