Organizations increasingly rely upon integrated and shared information systems and databasessuch as ERP systems and data warehouses. Such shared systems pose new and unique support challenges for systems professionals. A review of the literature reveals that comprehensive models to study the support of shared information systems do not yet exist. Based on the theory of communities of practice, and on the concepts of convergence and divergence of systems and practice, the boundary object brokering model of shared information systems is developed. This model is applied to an interpretive case study of a large company, illustrating how shared systems can be seen as boundary objects that connect disparate communities of practice. The model and case study show how the traditional role of systems professionals has been augmented to include brokering tasks, providing new issues and implications for theory and practice.