The World Health Organization has labeled the problem of arsenic contamination of groundwater in South Asia as “the largest mass poisoning in human history.” Various technical solutions to the problem fall into one of two broad categories: (i) cleaning contaminated water before human consumption and (ii) encouraging people to switch to less contaminated water sources. In this paper, we review research on the behavioral, social, political, and economic factors that determine the field-level effectiveness of the suite of technical solutions and the complexities that arise when scaling such solutions to reach large numbers of people. We highlight the conceptual links between arsenic-mitigation policy interventions and other development projects in Bangladesh and elsewhere, as analyzed by development economists, that can shed light on the key social and behavioral mechanisms at play. We conclude by identifying the most promising policy interventions to counter the arsenic crisis in Bangladesh. We support a national well-testing program combined with interventions that address the key market failures (affordability, coordination failures, and elite and political capture of public funds) that currently prevent more deep-well construction in Bangladesh.