Models of work processes and of organizations’ activities are an important part of workfiow systems and simulation, and capture procedural knowledge stored within the organization. However, acquiring, maintaining, and customizing these models can be difficult. To assist the acquisition and maintenance of organizational models, we have developed a set of knowledge-acquisition tools suitable for use in the domain of medical organizations. In modeling medical organization processes, three areas of expertise must be brought together. Expertise in medical care, organizational structure, and modeling is necessary to describe accurately the process of medical care delivery for simulation or workflow management. We propose a method of modeling work processes that uses the Protege suite of tools to generate organization-specific work process descriptions. We have created a set of Protege knowledge- acquisition tools customized for medical, organization, and modeling experts, and have used a prototype system to create detailed, site-specific process descriptions. In our prototype system, we have identified a set of transformation operators that should make possible additional computer-based support. We believe this methodology will improve acquisition of an organizational model, and make it easier to maintain an accurate model in the face of changes in medical process or organizational structure.