While the use of information technologies is becoming increasingly widespread in healthcare organizations, such as large hospitals, to date these organizations lack unified information systems providing a comprehensive view of the organization's state. We define a technique for building formal models capturing the state of hospital departments and the interactions among departments during hospital operations. These models, based on Petri nets, will support a variety of management and decision-support tools, such as statistical analysis, simulation, and dynamic reconfiguration. These models are at the core of a new software prototype that we are developing for the University of Illinois Medical Center at Chicago.