High level ab initio calculations performed at the G2 level have been used to characterize the potential energy surface for rearrangement and fragmentation of [CH3CH2OCH2](+). Ion-neutral complexes play a crucial role in the lowest-energy decomposition leading to elimination of water. RRKM calculations on the G2 surface are found to give results consistent with the experimentally observed metastable ion elimination products and with the results of various deuterium-and C-13-labeling experiments. The consequences of producing [CH3CH2OCH2](+) by isomerization from [CH3CHOCH3](+) and of producing [CH3CH2CHOH](+) by isomerization from [CH3C(OH)CH3](+) in relation to the rearrangement/fragmentation behavior are examined and found to be nicely consistent with experimental observations. Experimental thermochemical quantities such as rate-limiting barriers and heats of formation are found generally to be in good agreement with calculated values.