This study examined the potential economic impacts in the United States of the commercial adoption of a corn rootworm (CRW) resistant transgenic corn. Using a counterfactual approach, we estimated that if the technology had been made available in the year 2000 at a price that would equate per acre costs to those for insecticide-based corn rootworm control, and adopted on all of the acres treated for corn rootworm in that year, the total benefits would have been $460 million. This benefit includes $171 million to the technology developer and seed companies, $231 million to farmers from yield gains, and a further $58 million to farmers from reduced risk, time savings, and other nonpecuniary benefits associated with reduced use of insecticides. This is a one-year benefit with 100 percent adoption. Our nation-wide survey of corn producers suggests that initial adoption might be as low as 30 percent, which means that the first-year benefits might be only one-third of the value implied by 100 percent adoption. Different pricing assumptions would mostly change the distribution of the benefits between farmers and others, so long as the pricing did not influence the adoption rate as well. Benefits over time would reflect changing adoption patterns and evolving insect resistance. Further analysis could include the effects of any refuge requirements implemented to slow the development of resistance, when such requirements are known.