This paper begins to map the economic impact of discontinuing atrazine’s use, as some activists have suggested, in Illinois, the nation’s second-largest corn-producing state. The paper finds that without atrazine, grower incomes would decline between $159 million and $555 million due to use of more expensive and less effective alternatives, thus increasing costs and decreasing yields. Generally, an atrazine ban would have the practical effect of a new tax on corn growers. The paper also identifies numerous environmental detriments which would result from discontinuance of atrazine use.