Mizen Boushi means "proactive problem prevention" and refers to methods developed by Toyota for maintaining product reliability through the design and development process by anticipating and mitigating potential quality risks caused by proposed design changes. Mizen Boushi theory can be applied to production operations as well, to develop the highly reliable supply chain required by the Toyota Production System. Process changes in a high volume environment occur more frequently than product design change proposals, and can be either planned or unpredictable; the theory suggests that changes should be avoided to maintain relaibility. Using Mizen Boushi theory, the authors develop a framework for maintaining process and product reliability in a dynamic mass production environment, and then test the framework using case studies from a North American auto parts supplier. The proposed framework can help an auto parts supplier develop an organizational capability for relaibility that can lead to competitive advantage in today's global marketplace.