Arsenic contamination of groundwater is widespread in south and southeastern Asia with an estimated 100 million people impacted world-wide.  While second to drinking water in terms of exposure, arsenic entry into rice plants and ultimate storage in grains represents and important route of As exposure particularly on a global level.  Rice plants are more susceptible than other grains to accumulate arsenic because they are typically grown under flooded conditions where arsenic is mobilized as iron (hydr)oxides reductively dissolve, and both As(V) and As(III) are absorbed by rice roots due to their similarities with plant nutrients (phosphate and silicic acid).  Exacerbating As exposure to rice roots (and ultimately grain storage) is the practice of using As-laden groundwater for dry-season irrigation, thereby increasing As availability to plants more so than soil flooding alone.  Dry-season irrigation is a common practice in Bangladesh and West Bengal, which have received much attention in terms of grain-As research.  Other river systems in south and southeastern Asia are less-well studied in terms of As-rice relationships.  Here, we present a field sampling campaign aimed at understanding the soil-straw-grain relationship of As in rice from Cambodia, situated along the Mekong River.  Samples were obtained from Kandal and Prey Veng provinces, both of which are known to have elevated As in groundwater.  The results of this study illustrate the distribution of arsenic and the global exposure risk of arsenic to humans.