Decomposition of several environmental pollutants in water using perylene adsorbed on silica gel (Pe/SiO2 powder) as a photocatalyst under the visible-light irradiation have been studied. The Pe/SiO2 powder was prepared by mixing a toluene solution of the perylene with silica gel followed by evaporating the toluene. Irradiation by visible light (>420nm) of the methyl orange aqueous solution with the Pe/SiO2 powder in the presence of ascorbic acid resulted in the decomposition of the methyl orange. The rate of decrease of the methyl orange reached 99% by visible light irradiation for 20min. The reaction also occurred by the irradiation of sunlight. In addition, the irradiation of visible light also led to the decomposition of imidacloprid using Pe/SiO2 in the presence of ascorbic acid. Furthermore, irradiation by visible light (>420nm) of a pentachlorophenol aqueous solution with the Pe/SiO2 powder resulted in the decomposition of the pentachlorophenol. The possible mechanisms of these reactions are discussed.