Three polymorphs of Ga2O3 (alpha-, beta-, and gamma-Ga2O3) were prepared, and their photocatalytic activities were evaluated by the decomposition of volatile aromatic compounds (e.g., benzene, toluene, and ethylbenzene) in dry air stream under UV light illumination at room temperature. It was found that the Ga2O3 catalysts exhibited much higher photocatalytic activity than commercial TiO2. The photocatalytic activities of the Ga2O3 polymorphs were strongly influenced by their crystal structure, and their specific activities decreased in the following order: beta-Ga2O3 > alpha-Ga2O3 > gamma-Ga2O3. The reasons for the differences in photocatalytic activity of the Ga203 polymorphs are discussed in terms of crystallinity, geometric structure, and electronic properties of the polymorphs. (c) 2007 Elsevier Inc. All rights reserved.