Among a number of structures made of or related to soil, the objects in the seismic design code are foundations, earth-pressure-resisting structures, embankments and open-cutting tunnels. Since all these structures were damaged heavily by the Hyogoken-Nambu Earthquake, it has become an urgent issue how to safely design structures. For drawing up a seismic design code of structures concerned with soil, the most important task is to understand how the structures are supported by soil. Then, the interaction between soil and structures should be evaluated exactly. This paper describes the basic considerations for the new seismic design code.