Based on the "polymer-cation templates" technique, well-defined BaMoO4 hollow spheres with an average diameter of 2.3 mu m have been synthesized via a simple precipitation reaction between BaCl2 and (NH4)(6)Mo7O24 center dot 4H(2)O at room temperature in the presence of poly(methacrylic acid). The size of the hollow spheres could be tuned down to 1.5 mu m by decreasing the concentrations of Ba2+ or MoO42- in the reaction solution. Compared with current fabrication routines for hollow spheres, this method is facile and cost-effective as no surfactant is needed, and can be applied to produce other inorganic hollow-structured materials.