Well-defined superstructures of rectangular- shaped BaCrO4 and extensive network of BaCrO4 nanoparticles constructed by self-assembly were prepared in cetyltrimethylammonium bromide (CTAB) reverse microemulsions. The effects of aging time and reactant concentrations on the morphology and the self-assemble pattern of the nanostructured BaCrO4 were investigated. TEM combined with the electron diffraction was used to characterize the morphology and the crystal structure of the prepared nanostructured BaCrO4 at different conditions. (C) 2004 Elsevier B.V. All rights reserved.