Content and Language Integrated Learning (CLIL) is one of the most recent and most innovative phenomena in education at the moment. Since this approach is still very new, only a few suitable teaching materials have been published for the various school subjects. In some countries, however, there are dedicated CLIL teachers and linguists who have already developed CLIL-specific textbooks for certain content subjects (e.g. Geography, History or Biology). In this thesis, a theoretical analysis and practical evaluation of the CLIL teaching materials "Cross-Curriculum Creativity – Biology" (Books 1-4) (Fierling & Machotka 2008) was carried out. These textbooks are intended to be used to teach Biology in English. They follow the Austrian curriculum for Biology for the first form of secondary education (i.e. for children aged ten to twelve). Overall, the examination showed that while the books are a good basis for CLIL teachers who intend to teach Biology in English in Austria, there is still room for improvement.