Arsenic is known as the king of poisons and had plagued human being since the days of antiquity. It is both a cause of large-scale environmental contamination and serious health hazard. Incidences of arsenic contamination in ground water and the subsequent sufferings of people from arsenic poisoning resulting from drinking arsenic contaminated water have been widely reported in the developed and developing countries. Instances of arsenic contamination in the world are mainly of two categories: (a) natural groundwater contamination; and (b) contamination of water, air and the environment caused by the use of arsenical pesticides, industrial activities, mining and smelting operations. The focus of this book prominently encompasses the information on aquatic chemistry of arsenic (including analysis and removal studies) with particular reference to drinking water and the researches carried out worldwide by different organizations. Special reference has been made in this book to the recommendations of WHO, which has contributed significantly in providing financial, technical and manpower support to resolve this global environmental menace of arsenic in groundwater. The information presented in this book would hopefully serve as a valuable material for the scientists and professionals engaged in this subject area.