One of the widely held opinions about Japanese firms’ high performance suggests that Japanese employees, organized in teams, are making kaizen (continuous improvements) in their own jobs through quality circles or other initiatives such as a suggestion system. But who are these employees? They would have to be blue−collar workers in the Western perception, but the part of their contribution in improving productivity and price cost does not seem exceed 10% of all improvements obtained. Who then brings about the major part of these improvements? Are the kaizen activities carried out without having relation to the company’s profit strategy? If the employees have an objective in their kaizen activities, who provides the objectives? What do these objectives consist of? How are their activities managed? These questions invite us to inquire about a whole
management system of kaizen at Toyota Production System, considered as the basic model of “Lean Production”. But Toyota reoriented its organized kaizen activities toward the construction of more humanized production system during 1990s. This paper then shows this reorientation and the new direction by showing the case of Tahara No.1 plant. Through these discussions, I want to emphasize the importance of organized kaizen activities that group leaders, chief leaders and engineers are carrying out, and also the fact that their activities are now centered not only upon productivity increase but also upon the humanization of work.