This paper aims to study methyl tert-butyl ether (MTBE) degradation in the presence of ultraviolet (UV) light and hydrogen peroxide, and to determine the effects of operating conditions on the reaction kinetics. Two key parameters investigated in this study include the concentration of hydrogen peroxide and the average UV light intensity in the solution. A 1000W xenon arc lamp was used as the light source. The degradation of MTBE was found to follow a pseudo-first-order kinetics in terms of MTBE concentration. Although reaction rate increased with the addition of hydrogen peroxide, higher levels of hydrogen peroxide had a diminishing return since the excessive hydrogen peroxide could act as a scavenger for the hydroxyl radicals. On the other hand, the average UV light intensity in the solution was found to proportionally increase the reaction rate constant. A regression model was developed for the pseudo-first-order rate constant (k) as a function of the hydrogen peroxide concentration and the average light intensity in the solution: k = 8.33 x 10(-3) I-avgH[H2O2](0.7) (0.15 g/L<[H2O2]<0.62g/L) with a correlation coefficient of 0.93. This model was used to estimate MTBE degradation rate in the UV/H2O2 process. (C) 2004 Elsevier Ltd. All rights reserved.