This paper reports the synthesis and characterization of nanocrystalline ZnO powders by a simple method using zinc acetate dihydrate and polyvinyl pyrrolidone (PVP) as a chelating agent. The polymeric precursor was characterized by TG-DTA to determine the thermal decomposition and crystallization temperature which was found to be at 600 degrees C. The precursor was calcined at 600 degrees C for 1 h to obtain nanocrystalline ZnO powders. The morphology and crystalline size of the calcined powders characterized by SEM and TEM revealed that the powders consisted of the mixture of nanoparticles with particle sizes of similar to 50-100nm and nanorods with diameters of similar to 100-200nm and 200-500nm in length. The XRD and FT-IR results indicated that the synthesized ZnO powders had the pure wurtzite structure with lattice parameters a and c of 0.32344 +/-0.00058 and 0.51843 +/- 0.00211 rim, respectively. The synthesized powders exhibited the UV absorption at around 2.99eV with the estimated direct bandgap (E-g) of 3.10eV. Room temperature photoluminescence spectrum of the powders showed a strong UV emission band at similar to 2.98eV, a weak blue band at 2.82eV, a week blue-green band at 2.56eV, and a weak green band at 2.34eV, which indicated their high structural and optical quality. (c) 2005 Elsevier B.V. All rights reserved.