ABSTRACT: This paper is based on the oral presentation with the same title, given at the Aveiro Course on Geotechnical Risk in Tunnels in 2004. The main part of this paper consists of a review of recently published material on the DAT (Decision Aids for Tunnelling) which give a general description and show the application in the Swiss Transalpine tunnels both before and during construction as well as an application to assess different tunneling technologies. The possibility to update the information and resource management are also discussed in this context. Finally, two cases in Korea are presented in which the effect of exploration and of different construction methods are described.