Asia has long history and tradition of timber-based post and beam construction. However, in the Japanese building regulation, application of traditional construction has been limited to small buildings mostly for dwellings. This unvalued recognition of traditional construction is attributed to the lack of engineering research in its structural fire safety, especially on load-bearing assemblies such as wall timber frames and beam-floor complexes. For the application of such construction to large public buildings, it is necessary to make the load-bearing assemblies sustainable during a fire and rated as Quasi-fireproof construction in the Japanese building regulation*1. Also, because of the openness typical in the planning of Japanese traditional buildings, it is necessary to verify the fire resistance of load-bearing interior walls exposed to both-sides fire heating. Such study is needed also for the fire protection of historic heritage timber buildings widely distributed in Asia. This work intends to develop predictive and design method for the principal structural members of traditional timber construction. The present report is a summary of a comprehensive study, and includes the following studies: 1. Modeling of char layer formation and fields of temperature and Young's modulus within column and beam due to fire exposure based on a series of small scale unloaded fire tests 2. Development of predictive method for the mechanical performance, especially the buckling criteria, of the load-bearing assemblies based on the char and temperature field modeling 3. Validation of the predictive method against full-scale loaded fire tests Finally guideline is proposed for the achievement of the Japanese Quasi-fireproof construction based on the traditional timber construction.