Biodegradation of MTBE under various multi-substrate conditions by Pseudomonas aeruginosa was investigated in this research. The addition of BTEX in various combinations significantly inhibited MTBE biodegradation. This result was mainly due to the non-competitive inhibition between MTBE and BTEX compounds. The rate of MTBE biodegradation decreased with the increasing substrate number for multi-substrate conditions. Additionally, the kinetic models developed in this research successfully simulate the degradation of MTBE under various multisubstrate conditions. However, the accumulation of TBA during MTBE biodegradation revealed that P. aeruginosa was unable to degrade TBA during the period of time tested. (c) 2007 Elsevier Ltd. All rights reserved.