The road mileage user-fee is viewed as a promising alternative to the fuel tax, which in recent years has proven to be an inadequate means of financing road infrastructure. Public opposition is often thought to be a barrier to the political feasibility of the road mileage user-fee, but there has been only limited empirical evidence to quantify this opposition and identify factors that may be driving it. We use a nationally representative public opinion survey to investigate the level and intensity of support for replacing the fuel tax with a mileage user-fee. Our results confirm that there is widespread public opposition to the adoption of mileage user-fees, with the number of opponents exceeding the number of supporters by a ratio of 4 to 1. Furthermore, public support for the mileage user-fee is largely independent of individual demographic characteristics but is sensitive to features of the mode of administration. Administration modes that improve public acceptability are those that minimize privacy intrusion, one-time technology costs, and tax evasion concerns, and maximize convenience, accuracy, and fairness. The intensity of opposition is stronger than the intensity of support; relative to supporters, those who oppose the mileage user-fee are more likely to state that they are willing to take political action against the adoption of mileage user-fees. Policy implications and suggestions for future research are discussed.