In this paper we present an overview of SHAMASH, a process modelling tool for business process reengineering. The main features that differentiate it from most current related tools are its ability to define and use organisation standards, and functional structure, and make automatic model simulation and optimisation of them. SHAMASH is a knowledge-based system, and we include a discussion on how knowledge acquisition did take place. Furthermore, we introduce a high level description of the architecture, the conceptual model, and other important modules of the system. q 2002 Elsevier Science B.V. All rights reserved.