Photocatalytic decomposition of gaseous benzene at room temperature was studied with a fixedbed annular reactor using titania as the photocatalyst. The effects of humidity, UV light intensity and benzene concentration on the conversion and mineralization of benzene were presented. Experimental results can be adequately described by using the Langmuir-Hinshelwood (L-H) kinetic model. The concentration distribution of benzene in the annular reactors of various dimensions can be described by combining the reactor design equation with L-H kinetics. Deactivation of catalyst was observed and attributed to the adsorption of reaction intermediates on TiO2 surface. The deactivated TiO2 catalyst could be photochernically regenerated by ozone-purging in the presence of humidity. (C) 2003 Elsevier B.V. All rights reserved.