In order to incorporate products developed under non-QbD approaches into company system based on the ICH vision, product and process knowledge gained by the QbD approach is necessary. To gain such knowledge, common appreciation of the need among the stakeholders in the company, collaboration among the company's functions, and operational issues relative to resource allocation are identified as challenges. Current situations and risk associated with the existing products are assessed. The risks include not only risks to quality/production, but also risks to the regulatory aspects under the current trend for regulatory discussion. Necessity of the application of QbD to exiting products is discussed. A case study for a 16 year-old exiting product is presented. The case study includes processes of verification of CQAs from the development and manufacturing data, data mining, additional experiments, recommendation for improvement and re-construction of control strategy. A number of regulatory change application approaches based on the case study are presented. A company wide data handling system to implement ICH Q8 approaches to existing products is discussed. Both the short-term approach prompted by a change proposal and the long term approach to promote continual improvement are presented. Finally, QbD approaches to existing products are summarized. As QbD approach to new products and QbD approach to existing products are compared, the two approaches have mostly common themes. In conclusion, this study highly recommends the QbD approach in commercial manufacture. This study has been conducted between 2009 and 2011 and the result was presented at a seminar held on October 4, 2011 in Tokyo.