Gold nanoparticles (partially below 5 nm in diameter) were successfully deposited on hexagonal and monoclinic WO3 supports by deposition-precipitation, which had been considered previously not feasible owing to the low isoelectronic point of WO3. The catalysts were characterized by TEM, SEM, N-2-adsorption, XRD, and XPS. In CO oxidation m-WO3/Au showed better catalytic activity over 100 A degrees C than h-WO3/Au. This was explained by that m-WO3 had higher surface OH coverage, resulting in larger Au nanoparticle loading and thus better catalytic activity.