Reengineering business processes seems to be a necessity in order to survive and prosper in today's competitive world. To support business process reengineering (BPR) efforts, we propose a framework based on high-level Petri nets. This framework is used to model and analyse business processes. The use of high-level Petri nets provides us with advanced analysis techniques and sophisticated software tools. To support the use of this Petri-net-based framework, we also present the "What, how and by whom?" approach. This approach has been developed to guide the application of the framework in a BPR setting. The "What, how and by whom?" approach identifies three important stages in the (re)design of a business process. By passing through these stages we obtain a complete Petri net model of the current (As-is) or proposed (To-be) situation, whereupon Petri-net-based analysis techniques can be used to verify the correctness and estimate the performance of the (re)designed business process.