Flexible workflow systems are needed for processes that need consistency as well as flexibility (e.g., personalized client interactions). A methodology for designing flexible service processes (FSP) and for implementing them as workflows is outlined. The development, continuous improvement and application of this methodology are analyzed in the framework of business process management. The outcome is the proposed FSP methodology process. The FSP methodology including its processes was developed in a consulting project. Business process modelling for flexibility would be greatly facilitated by tools that allow users to compose processes modularly and to check their consistency. A possible solution to this problem was worked out and successfully used for client expectation management. For our client organization, the proposed change was a radical development process reengineering. For this change, we identified the key success soft-factors first. Then we developed the FSP methodology pr...