There is growing interest among hospitals in reengineering. It promises dramatic improvements in performance: Costs will be reduced while work processes, productivity, and patient care will all improve. A review of the health care literature on reengineering shows that little evidence exists to support its claims. This article critiques the existing literature on reengineering and addresses the conundrum hospital executives encounter when faced with the decision to adopt a new management technique--such as reengineering--in the absence of proof of its efficacy.