The diffusion of clinical guidelines to describe the proper way to deal with patients? situations is spreading out and opens new issues in the context of modeling and managing (temporal) information about medical activities. Guidelines can be seen as processes describing the sequence of activities to be executed, and thus approaches proposed in the business context can be used to model them. In this paper, we propose a general conceptual workflow model, considering both activities and their temporal properties, and focus on the representation of clinical guidelines by the proposed model.