With the rapid advance of information technology (IT), many organizations are implementing IT to enhance their business processes efficiency intra- and inter-organizations. Prior to deploying the appropriate IT, conducting business process reengineering (BPR) has been considered to be the most important first step. Over the past two decades a considerable effort has been made in BPR implementation in practice. However, the detailed guideline for the BPR implementation is lacking. To alleviate the forgoing problem, the A-company was chosen for this study which had undergone the BPR implementation with the help of two well-known consultant firms. We followed the case study method to investigate what activities were performed when the A-company implemented BPR, how consultants interacted with the A-company in these activities, what input and output were needed, and what methods or models they used during each BPR step. Finally we proposed a comprehensive methodology which has detailed guideline for BPR implementation. With this proposed methodology, the implementing organization can have better understanding and preparation for BPR implementation, and thereby enhance the efficiency and effectiveness of BPR implementation.