In Bangladesh, rice is boiled with an excessive amount of water, and the water remaining after cooking will be discarded. We did an on-site experiment to assess the effect of this cooking method on the amount of arsenic retained in cooked rice. The concentration of arsenic in cooked rice was higher than that in raw rice and absorbed water combined, suggesting a chelating effect by rice grains, or concentration of arsenic because of water evaporation during cooking, or both. The method of cooking and water used can affect the amount of arsenic in cooked rice, which will have implications for the assessment of the health risks of arsenic.