Restricting or eliminating the use of atrazine in the Midwest would have important economic consequences for farmers, consumers, and the environment. These consequences can only be evaluated with cooperation between economists and weed scientists. The weed control choice set available to farmers cannot be observed through deductive research. Economists and weed scientists worked together to identify all possible weed control strategies for corn and sorghum in the Midwest and to incorporate them into an economic model. An atrazine ban was found to be the costliest strategy, and a targeted, water-quality based strategy the most cost effective.