Decisions are being made by groups with increasing frequency, requiring that individuals collaborate within teams. In order to do so, the team must create a shared mental model of its goals and processes. Communication has been shown to play a fundamental role in the development and evolution of this model as well as in the achievement of team goals. Previous research has established that roles within teams are well-defined and that each team member is familiar with them, that communication is most frequent among those whose tasks are most interdependent and interrelated, and that communication centers around attaining team goals. This study addresses the structure of team collaboration and the role of communication in maintaining the structure of an out-patient primary care unit at Beth Israel Deaconess Medical Center in Boston, Massachusetts. A work and activity analysis showed that individual roles are clear and distinct and part of the shared mental model of the team, reducing redundancy and omission of goal-directed tasks. Communication was found to be more frequent among team members with related tasks and with more similar models of practice. Communication topics were found to be related to team goals. The importance of the shared mental model and of communication in the collaborative process is emphasized. Different domain experts working together in a collaborative way complement each other through this shared understanding, maximizing the efficiency and the effectiveness of the process and outcome.