In the past decades, international data base on radon (Rn-222) has been improved steadily. However, representative data on thoron (Rn-220) are still few. For evaluation of the behavior and concentrations of environmental thoron, its exhalation rate from soil and buildings materials is considered as an important parameter. In this study, a simple and quick method was developed to measure the exhalation rate of thoron from soil and building materials. The results found that the exhalation rate of thoron is largely affected by the water content in soil surface. High exhalation rate of thoron was observed in the traditional Japanese house with mud and wood as building materials. 11th International Congress of the International Radiation Protection Association