Reengineering is also an improvement process. However, it does not assume the existing structure or framework is correct, rather asks broader questions. Hammer defines reengineering as "Fundamental rethinking and radical redesign of business process to achieve dramatic improvements in critical measures of performance such as cost, service, and speed." Reengineering is complimentary to quality. Reengineering in episodic and it is used to achieve massive breakthrough. Reengineering challenges the assumption that governs a work process.
Reengineering is used when the situation is drastic, when incremental improvements are inadequate to meet the needs of the situation or when the organization wants to “start over”. Reengineering establishes a new staring point and a new standard of performance for a given process, which is later continuously improved using quality improvement monitoring and techniques.