In Ganga-Brahamaputra plain of India (population ~ 500 million) about 80% people use groundwater for drinking and other domestic purposes. Contamination of groundwater due to naturally occurring arsenic (As) has caused chronic As poisoning leading to cancer and non-cancerous effects in the state West-Bengal, India for last three decades. This book features a detailed groundwater As contamination scenario in West Bengal - the 2nd largest population at risk from As toxicity after Bangladesh. The study categorizes the groundwater As scenario into 3 classes: severely, mildly affected, and As safe zones based on 1,35,555 groundwater sample analysis. Further, it highlights identification of arsenicosis patients based on skin lesions and associated symptoms; temporal/seasonal variability trends; development of analytical method for As speciation; As in raw and cooked rice and how cooking method can influence the final As content in rice that is being consumed. Finally this book recommends remediation approaches to combat the current As crisis. This research work was submitted for the degree of doctor of philosophy(Ph.D) at Jadavpur University,India and the degree was awarded in 2007.