Arsenic contamination of groundwater has been recognized as a great threat to water supply and public health in many countries in the world. This publication is intended to update the knowledge base in all aspects of arsenic contamination keeping Bangladesh in the focus. All the major issues such as hydrogeology, water, soil, food contamination, health and social consequences, analytical aspects along with chemistry and fate of arsenic in the environment has been discussed at length in the context of Bangladesh. This publication is a continuing endeavor of ITN-Bangladesh to disseminate information pertinent to water supply issues of national and international importance.