Nanometer materials of rare earth mixed oxides REFeO3 (RE = Sm, Eu, Gd) with the structure of perovskite-type were synthesized by the sol-gel method in the citric acid system. The structure and crystal phase of the powders were characterized using an X-ray diffractometer. The shape and size were analyzed using a JEM-100X transmission electron microscopy. The perovskite-type oxides were spherical with the mean grain size of 28, 20 and 21 nm, respectively. Their crystal structures showed a certain amount of lattice distortion due to the decrease of grain size and the increase of surface area. The photocatalytic activities of these three materials were studied for the degradation of various water-soluble dyes. The effect of catalyst loading on the photocatalytic activity was also investigated. SmFeO3, EuFeO3, GdFeO3 exhibited high photocatalytic activities and the increase in catalyst loading could improve their photocatalytic activities. (c) 2005 Elsevier B.V. All rights reserved.