The preservation district of groups of traditional buildings is an important category of cultural properties in Japan. Japan has entered an earthquake active period. However, conventional culturally and socially oriented site investigation methods hardly satisfy the requirements of risk management of district preservation. In this study, the authors introduce an investigation method from the structural and security perspectives. They explain the study procedure, methods and results. Results of the investigation of two coastal districts, namely, Ine and Yuasa, are comparatively studied, and regional disparities are highlighted. The study concludes that district vulnerability and house structural performance should be considered as important indices when making decisions regarding district preservation.