Well-aligned ZnO rod arrays have been successfully synthesized on glass substrate from the aqueous solution of Zn(NO3)(2)center dot 6H(2)O and C6H12N4 (HMT). Some critical issues such as seed layers, concentration and reaction time were investigated. The results show that ZnO seed layers were pre-requisite for the aligned growth of ZnO rod arrays. The length of rods is tunable in a range from 2 mm to 3 mm by varying the solution concentration and reaction time. X-ray diffraction results demonstrate that ZnO rods are wurtzite crystal structures preferentially orienting in the direction of the c-axis. Microstructure observation by scanning electron microscope confirms that ZnO rods grew up perpendicular to the substrate. Room-temperature photoluminescence (PL) spectrum of rod arrays shows a strong emission band at about 396 nm. (C) 2007 Published by Elsevier B.V.