The alkali-silica reaction is an unusual and unpredictable phenomenon which occurs worldwide. The factors involved are exceedingly complex, very interdependent and highly interactive. We are now beginning to realise that external agents, environmental conditions and microclimates can have as much of an influence as the basic ingredients of the reaction, and that the timescale over which ASR occurs can be extremely broad. Because of the obvious and serious implications for the durability and integrity of concrete structures and components, there is a need to review the fundamental causes and spectrum of effects of ASR. This book considers the advances that have been made in our understanding of this problem throughout the world.