More than 40% of U.S. corn is now consumed in the production of ethanol. With the United States by far the world’s largest producer and exporter of corn, this represents an estimated 15% of global corn production. A recent survey by the National Academy of Sciences estimated that globally biofuels expansion accounted for 20-40% of the price increases seen in 2007-8, when prices of many food crops doubled. This had a dramatic impact on poor consumers and on net-food-importing developing countries. Expanding U.S. production and consumption of corn-based ethanol, which has been encouraged by a range of U.S. government subsidies and incentives, is considered one of the most important biofuel programs in putting upward pressure on food prices. Mexico now imports about one-third of its corn from the United States. Using conservative estimates from a study on U.S. ethanol expansion and corn prices, we estimate the direct impacts of U.S. ethanol expansion on Mexican corn import costs. We find that from 2006-2011, U.S. ethanol expansion cost Mexico about $1.5 billion due to ethanol-related corn price increases. Other methodologies suggest the costs could be more than twice as high, surpassing $3 billion over the period.