This thesis deals with the possibilty of cancelling a contract through act of God, based on the view of a traveller and a travel business. There is a legal regulation (§651j BGB) in Germany, but only a general law of contract in Austria, due to this fact the main aim was to create a comparison between German and Austrian law. After a short definition about the basics of German and Austrian tourism law in the first part of the thesis, the second part deals with the requirements of cancellation law in both countries. The third chapter is dedicated to different groupcases based on the act of God and includes some examples according to judicature. The fourth part treats legal consequences and effects in case of cancellation of contracts. Finally every chapter results in a short comparative lay analysis and emphasizes the differences between Austria and Germany. As a conclusion the fifth chapter contains a summary of results.