A solvothermal route has been successfully used to prepare hexagonal (NH4)(0.33)WO3 directly from yellow monoclinic WO3 powders in pyridine at 350 degrees C. The as-prepared product was dark blue, which was characterized by the X-ray powder diffraction (XRD) method, transmission electron microscopy (TEM), and X-ray photoelectron spectra (XPS). XRD shows that phase-pure hexagonal (NH4)(0.33)WO3 has been prepared. TEM images show that the particles are in the shape of columns. XPS measurement indicated that the chemical state on the surface of (NH4)(0.33)WO3 is similar to that of (NH4)(6)W7O24H2O.