The Ganges-Meghna-Brahmaputra groundwater aquifer, which is contaminated with As, is the sole source of drinking water and also a major source of irrigation water in Bangladesh. Approximately 60% of the 140 million people of Bangladesh are at risk from As-contaminated drinking water. An additional, long-term risk is the potential loss of agricultural sustainability. Intensive irrigation of rice, the staple food crop of Bangladesh, with As-contaminated groundwater is increasing the soil As level in many areas of Bangladesh. In a survey across Bangladesh we found severe As contamination in  south-western, central and south-eastern districts. A major concern, related to the vital issue of food security in the country, now, is whether high water-soil As is affecting rice production. We conducted a 2-year (2006 and 2007) irrigated winter rice (locally known as Boro) experiment in farmers’ fields in Faridpur, a badly As-affected district in the Gangetic Floodplain of central Bangladesh. A shallow tube well command area (water As, 130 µg L^-1) with soil As levels varying from 11 to 56 mg kg^-1 was selected to study the effect of naturally occurring As in irrigation water and soil on rice yield. In both years, the yield of a popular Boro variety, BRRI Dhan 29, decreased consistently and drastically from 7-8 t ha^-1 (rough rice) to 2-2.5 t ha^-1 as the soil As level increased from 11 to 56 mg kg^-1. This year (2007) we observed that with high total soil As, there could be enough bio-available As to adversely affect the growth and yield of relatively "safe" upland crops like wheat and maize. Using the national soil and irrigation-water As databases and results of the rice yield experiment, we predict substantial rice production decreases with continued use of high-As groundwater for irrigation. This study indicates the importance of developing As management technologies for sustainable crop production and a national policy of irrigation-water management in Bangladesh.