AbstractRandom regular graphs are, at least theoretically, popular communication networks. The reason for this is that they combine low (that is constant) degree with good expansion properties crucial for efficient communication and load balancing. When any kind of communication network gets large one is faced with the question of fault tolerance of this network. Here, we consider the question: Are the expansion properties of random regular graphs preserved when each edge gets faulty independently of other edges with a given fault probability? We improve previous results on this problem in two respects: First, expansion properties are preserved for much higher fault probabilities than known before. Second, our results apply to random regula...