Zinc oxide (ZnO) microrods were prepared at different substrate temperatures by ultrasonic spray pyrolysis technique on glass substrates. The X-ray diffraction patterns show that obtained rods are composed of wurtzite-type and mainly grow along the [0 0 2] direction. Scanning electron microscope images show that the diameters of ZnO rods and the distances among the rods increase with increasing substrate temperature. In addition, the optical measurements reveal that transmittance and the band gap energies of films increase with increasing substrate temperature. (C) 2007 Elsevier B.V. All rights reserved.