A detailed study in the Sahibganj district of Jharkhand state in the middle Ganga plain was carried out to determine the severity of groundwater arsenic contamination and related adverse health effects due to chronic arsenic exposure. Arsenic was analyzed by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) in water and biological samples in both contaminated and noncontaminated areas. Health effects in three villages where tubewells (n = 178) were highly contaminated (91, 79.8, and 42% above 10, 50, and 300 µg L-1) were determined. Analyses of a total of 367 biological samples (nail, hair, and urine) from affected villages revealed that an average 88% of samples contained arsenic above normal level. Out of 522 people screened from these three villages, 71 were registered with arsenical skin lesions. A case involving arsenical skin lesions resulting in cancer was noted during the study. A representative histopathological picture of skin biopsy was presented. Out of 40 children examined, nine were registered with arsenical skin lesions. A child of 18 months drinking arsenic concentration water 1150 µg L-1 displayed arsenical skin lesions, indicating arsenical skin lesions may appear earlier if arsenic concentration is high in drinking water. Different clinical and electrophysiological neurological features and abnormal quantitative sensory perception thresholds were noted amongst patients. Provision of safe water, better nutrition, and proper awareness about the arsenic danger to exposed population may save lives and avoid sufferings.