The gasoline additive methyl tert-butyl ether (MTBE) is considered recalcitrant to bioremediation. Formation of rate-limiting metabolic intermediates, enhancement or inhibition of degradation by co-occurring gasoline components, and influences of subsurface environmental conditions are among the factors that influence MTBE biodegradation in the natural environment. Although anaerobic biodegradation of MTBE is possible, the compound biodegrades most rapidly in the presence of oxygen. The authors review the following MTBE bioremediation strategies: ex situ ground-water treatment using either suspended growth bioreactors or fixed-film bioreactors, and in situ processes involving natural attenuation, bioenhancement (i.e., addition of electron acceptors, nutrients, or co-substrates), or bioaugmentation (i.e., addition of selected microorganisms to augment a site's indigenous hydrocarbon-degrading microbial population). Case studies illustrate each of these approaches.