Methyl tert-butyl ether (MTBE) is a synthetic additive to gasoline, which was developed as a substitute for organolead compounds, which cause air pollution by vehicle emissions. The presence of MTBE at a gasoline-contaminated site, however, complicates natural attenuation because MTBE plumes resist to biological degradation and can inhibit biodegradation of other fuel components. Chemical and physical properties of MTBE, its health effects and MTBE remediation technologies are summarized. A substantial part of the review is devoted to biodegradation of MTBE under various environmental conditions.