Emergency departments (ED) are prototypical complex environments. Physician activities in these settings are characterized as episodic, dynamic and collaborative. Using an exploratory study supported by observations, physician shadowing and interviews, we characterize the physician's activities in an ED including the nature of activities, the time allocated for these activities, how these activities are distributed across the unit and the susceptibility of these activities for interruptions. We found that approximately one-fourth (∼25%) of the physician activities (e.g., direct patient care) were localized at specific locations in the unit, while the rest of the activities (e.g., communication) were distributed across the unit and were less predictable. The non-localized activities had a likelihood of interruptions. The results have important implications for mitigating the physician workload, and the design of technologies for monitoring such complex settings.