The U.S. appears committed to the ongoing use of ethanol biofuels. In order to realize the desired benefits, ethanol production must continue to become more efficient. Although many technologies have emerged to improve efficiency this article focuses on the role that corn biotechnology might play. Biotechnology offers the potential to increase yields and lower input use as well as aid the conversion of corn to ethanol. This could have a meaningful impact on the energy balance and greenhouse gas emissions of ethanol production. This article finds those impacts to be significant, although likely to be eclipsed by cellulosic biofuels. However, the realization of any such benefits is conditioned by prevailing market and policy conditions. In a world where the market is less constrained by policy, increased yields afforded through biotechnology would increase corn production, which leads to lower corn price and larger ethanol production volume. When expected policies, most notably the Renewable Fuel Standard, are considered the impacts of biotechnology change. The Renewable Fuel Standard effectively limits the amount of corn based ethanol that is consumed as it shifts production towards cellulosic feedstocks. Despite the increase in corn production and reduced corn price there are only marginal increases in ethanol production volume. Accordingly, the RFSs support of competing biofuels might limit some dimensions of the ethanol industry including its ability to fully benefit from corn biotechnologies.