Portable water is one the most indispensable matter for human survival. A large number of populations depend on groundwater. The groundwater can be contaminated by naturally occurring arsenic .This book focuses on groundwater arsenic contamination, source and mobilization, toxicity and adverse health effects, analytical techniques for determination of arsenic, approached clinical methodologies, and social impact of arsenic contamination. Following the discovery of arsenic incident in Bihar, a detailed study has been conducted in 15 districts of Bihar and Uttar Pradesh by the side of the river Ganga. Patients with arsenical skin lesions (different form of melanosis,keratosis, Bowen’s, skin cancer etc.) ‘Arsenical’ neuropathy, obstetric outcome was diagnosed. Proper mitigation approaches involving surface water, rain water harvesting, dug-well, with proper treatment against bacterial and other contaminations. This dissertation work has been submitted for the degree of doctorate of philosophy of Jadavpur University. The book has been intended to improve understanding of the naturally occurring arsenic in groundwater and its health effects.