Bi2-xLaxAlNbO7 (0 <= x <= 0.5) photocatalysts were synthesized by the solid-state reaction method and characterized by powder X-ray diffraction (XRD), infrared (IR) spectra and ultraviolet-visible (UV-vis) spectrophotometer. The band gaps of the photocatalysts were estimated from absorption edge of diffuse reflectance spectra, which were increased by the doping of lanthanum. It was found from the electronic band structure study that orbitals of La 5d, Bi 6p and Nb 4d formed a conduction band at a more positive level than Bi 6p and Nb 4d orbitals, which results in increasing the band gap. Photocatalytic activity for water splitting of Bi1.8La0.2AlNbO7 was about 2 times higher than that of noncloped Bi2AlNbO7. The increased photocatalytic activity of La-doped Bi2AlNbO7 was discussed in relation to the band structure and the strong absorption of OH groups at the surface of the catalyst. (C) 2008 Elsevier Ltd. All rights reserved.