A considerable effort is continuing in the U.S. to develop and introduce into society alternatives to the use of conventional gasoline and diesel fuel for transportation. The primary motives for this effort are twofold: energy security and improvement in air quality-most notable ozone, or smog, formation. Fused silica flow reactor instrumentation coupled with in-line GC-MS analysis has been used to examine the high-temperature thermal degradation of methanol, ethanol, M85, and E85 under fuel-lean (oxidative), stoichiometric, and fuel-rich (pyrolytic) conditions. Experiments have been conducted at temperatures of 650°C and 950°C for gas-phase residence times of 0.85 s. Specific reactivities of M85 were observed to be substantially lower than for the other fuels. Several previously unidentified species were observed in these experiments which may or may not impact atmospheric reactivity assessments of these fuels.