The potential economic impact of herbicide‐resistant corn varieties in the USA was measured using a regional econometric model. Six adoption scenarios were evaluated from 1991 to 1996, assuming different costs and adoption rates. Complete control of weed losses, with a $13/acre technology substituting for current chemical herbicide costs, would increase aggregate corn production by 2 to 4%, lower corn prices by as much as $0.30/bushel, shift regional acreage slightly, and increase the sum of consumers' and producers' surplus. Wider adoption increases total benefits, and differential adoption is more profitable to early adopting regions.