The extent of tunnel refurbishment has increased constantly in recent years. The particular importance of meticulous and thought-out planning has been demonstrated on recent projects. The original drawings often provide an insufficient basis for design work and have to be checked, verified or supplemented by targeted investigation measures. A brief glance at the list of claims from a refurbishment project can clearly demonstrate the potential savings, which could have been produced by relatively cheap investigations. For the planning and design of the refurbishment of the first tube of the Tauern Tunnel, many staged investigation surveys were therefore carried out. The investigation measures carried out and their results and effect on the design and tender documents for the refurbishment of the existing tube of the Tauern Tunnel are described in this article. © 2010 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.