As more organizations undertake business process reengineering (BPR), issues in implementing BPR projects become a major concern. This field research seeks empirically to explore the problems of implementing reengineering projects and how the severity of these problems relates to BPR project success. Based on past theories and research related to the implementation of organizational change as well as field experience of reengineering experts, a comprehensive list of sixty-four BPR implementation problems was identified. The severity of each problem was then rated by those who have participated in reengineering in 105 organizations. Analysis of the results clearly demonstrates the central importance of change management in BPR implementation success. Resolutions of problems in other areas such as technological competence and project planning were also determined to be necessary, but not sufficient, conditions for reengineering success. Further, problems that are more directly related to the conduct of a project such as process delineation, project management, and tactical planning were perceived as less difficult, yet highly related to project success. This situation was also true for human resource problems such as training personnel for the redesigned process. These findings suggest that reengineering project implementation is complex, involving many factors. To succeed, it is essential that change be managed and that balanced attention be paid to all identified factors, including those that are more contextual (e.g., management support and technological competence) as well as factors that pertain directly to the conduct of the project (e.g., project management and process delineation). As one of the first pieces of empirical evidence based on a field study, this research emphasizes the importance of addressing BPR implementation within the broader context of organizational change in a complex sociotechnical environment.