U.S. crop producers derive substantial economic benefits from atrazine and the other triazine herbicides (simazine and propazine). These herbicides generate yield gains for U.S. crop farmers, and in many cases, also reduce total costs for herbicides. Atrazine, the most widely used triazine herbicide, is the keystone of herbicide-based weed control in corn and other regionally important crops in the U.S. Corn acreage, yields and prices have increased over time so that the 3- year average value of corn produced in the U.S. has increased more than 2.7 times, from $18.6 billion in 1990 to 1992 to $54.3 billion in 2008 to 2010. Over this same period, crop production practices also evolved, including the widespread adoption of transgenic crops and reduced tillage systems. Given these and other changes since previous economic assessments of the producer benefits from triazine herbicides, an updated economic assessment of the benefits of atrazine and the other triazine herbicides seemed warranted.