In contrast to the US, fuel oxygenates are generally used as octane enhancers in Europe rather than to increase the oxygen level in gasoline for a cleaner combustion. To achieve the high average octane ratings of European gasolines (95 RON), currently more than 2.5 Mt/a of fuel oxygenates, mainly methyl tert-butyl ether (MTBE) are used. Stimulated by the public discussion in the US, there is a growing awareness of groundwater pollution related to the use of MTBE as a gasoline component. Although the number of leakage and spill sites in Europe is supposedly lower than in the US due to earlier implementation of strict storage facility regulations, contamination of groundwater with MTBE is significant. Owing to the lack of a uniform European standard, however, the situation may vary considerably in different European countries. Recent survey studies in northern and central Europe on groundwater pollution by MTBE revealed background concentrations of up to 3 µg/L, and concentrations at point sources of up to 500 mg/L. For southern and eastern European countries there is no data available to us on regulations or MTBE levels in the environment. Due to growing concern regarding groundwater pollution by MTBE, alternative octane enhancers are put forward in some European countries. While the dialkyl ethers tert-amyl methyl ether (TAME) and ethyl tert-butyl ether (ETBE) are already in use, the introduction of ethanol is being discussed.