Book excerpt: This book consolidates much of what is known about the geochemistry of arsenic and provides new information on relationships between high concentrations of arsenic in ground water and geochemical environments. The subject matter of this book ranges in scope from molecular-scale geochemical processes that affect the mobility of arsenic in ground water, to arsenic contaminated ground water at the national scale. Chapters were contributed by an international group of research scientists from a broad range of backgrounds.