Abstract
The concept of metropolitan area is the mono-centric, centripetal, nodal region for understanding and planning modern urban areas which have rapidly grown. However, the recent researches on the multi-nucleation or suburban downtowns of major metropolitan areas in United States or Japan, found another functional region with interdependency rather than hierarchy. Suburban downtowns appeared in American major metropolitan areas around 1990. On the other side, the realms around the downtowns in a metropolitan area show not independence but various flows between them. Japanese major metropolitan areas also have increased interdependent flows between suburbs hidden below the strong centripetal flows to central city. But nowadays, commuters to the central city are decreasing even in the Tokyo metropolitan area in the drastically changing social situation in Japan. It is this functional region composed of interdependent flows between realms or suburbs in common to metropolitan areas in US and Japan, that is new millennium regional concept just same as the nodal region in 20th century. And this new point of view is also important for the current urban policy of compact cities. Because a metropolitan area should be changed to a new urban area, which has some compact cities and people lived in this area has high mobility and various demands to the centers. The regional structure composed of these compact cities is therefore very crucial.
