Hot-electron-induced photodissociation of H-2 was demonstrated on small Au nanoparticles (AuNPs) supported on SiO2. The rate of dissociation of H-2 was found to be almost 2 orders of magnitude higher than that observed on equivalently prepared AuNPs on TiO2. The rate of H-2 dissociation was found to be linearly dependent on illumination intensity with a wavelength dependence resembling the absorption spectrum of the plasmon of the AuNPs. This result provides strong additional support for the hot-electron-induced mechanism for H-2 dissociation in this photocatalytic system.