MTBE is very water soluble and does not absorb appreciably to soil. It is also essentially non-biodegradable and non-reactive in water. Product studies were conducted to elucidate degradation pathways of MTBE, di-isopropyl ether (DIPE), ETBE, and TAME under the irradiation of ultrasound. All experiments were performed under oxygen gas saturation. The degradation pathways were established for MTBE, DIPE, ETBE, and TAME in oxygen saturation atmosphere. Pyrolytic degradation of C-C bond or abstraction of α (or β-) hydrogen by •OH led to a carbon centered radical, which could react with oxygen molecule to give the peroxyl radical. Combination of two peroxyl radicals yielded the tetroxide, which will eliminate an oxygen molecule producing one oxygen centered racicals. These radicals reacted to form stable intermediates. Although all these ethers are readily degraded, significant amounts of acetone were produced, which requires extended irradiation times to degrade under oxygen saturation. This is an abstract of a paper presented at the 222nd ACS National Meeting (Chicago, IL 8/26-30/2001).