Today’s critical infrastructures become more and more massive and complex as well as dependent on other critical infrastructures. This increases the likelihood of a multiple infrastructural breakdown. The development towards a more complex society with an increasing degree of interdependencies implies that we need to understand why system complexity results in increasing vulnerability. To be able to predict any consequences of a multiple infrastructural breakdown we need to construct models of the systems being considered, potential sources of risk and the couplings to other systems that might provide insight into the dynamics of risk propagation. In particular there is a need for a modelling framework capable of describing the interdependencies between our critical infrastructures.