In the process of testing spent fuel casks, BAM is gaining a lot of relevant data regarding the quality level of ductile cast iron (DCI). The basic parameters governing the material behaviour of ferritic and ferritic pearlitic DCI are discussed and the development of container quality over recent years is summarised. The high quality level of German DCI containers is outlined. The effect of microstructure, sample size and loading rate on the fracture toughness of DCI is discussed in the second part of the paper. (author).