Arsenic, one of the most common environmental contaminants, is found in water, food, and air. Drinking water sources are a main concern because of the concentration of the inorganic forms of arsenic. While much of the research on the impact of arsenic has focused on its carcinogenic potential, several studies have suggested that arsenic poses a threat to human cognitive development. Deficits in learning and memory, particularly hippocampal-dependent tasks, following acute and chronic arsenic exposure have been reported for both rodents and humans. We recently studied hippocampal-dependent learning in adult mice whose mothers consumed 50 parts per billion (ppb) arsenic in drinking water during pregnancy and until offspring weaning. Our studies have found that adult offspring from mouse dams exposed to 50 ppb arsenic throughout pregnancy have a deficit in hippocampal fear-conditioned learning. Further, offspring from mothers who consumed arsenic were more likely to fail in an active avoidance task. These deficits did not appear to be due to a failure in motor activity or in attentive behavior since open field locomotion and novel object exploration were unchanged compared to control mice. These data suggest that prenatal arsenic damages associative pathways in the hippocampus and may result in cognitive deficits. Future work will examine the impact of prenatal arsenic on the signaling pathways within the hippocampus with particular focus on the corticotrophin releasing factor receptor.