The coordination of activities in a work context has been examined by many disciplines and in recent years the role of information systems and other artifacts has become increasingly prominent. The emergency department (ED) of a hospital in a large US city is used to study how information systems and other coordinating mechanisms affect how physicians choose to perform their work and how such choices can impact the ED’s overall operational performance. The study used direct observation of the work performed in the ED, interviews of physicians, nurses and other ED staff members, and the analysis of historical performance data. The key findings were that the existing coordination mechanisms are a mix of fixed and mobile, computer and paper-based information systems, and other artifacts. The workstyles adopted by physicians were shaped by incidental characteristics of these coordination mechanisms. Some workstyles appear to have adverse, albeit unintended, effects on aspects of the department’s operational performance.