This paper presents a component-based product line architecture for workflow management systems. The process followed to design the proposed architecture was based on Catalysis. Extensions were made to represent variability across the process. The domain of workflow management systems has been shown to be appropriate to the application of the product line approach as there are a standard architecture and models established by a regulatory board, the Workflow Management Coalition. In addition, there is a demand for similar workflow management systems but with some different features. The proposed architecture was evaluated with Rapide simulation tools. The evaluation was based on selected scenarios, thus, avoiding implementation details.