A convenient precursor-calcination strategy is developed to fabricate hierarchical flowerlike ZnO superstructures from a hydrothermal synthesis combined with subsequent calcination without using any organic additives or surfactants. The samples were characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), thermo gravimetric-differential thermal analysis (TG-DTA) and N-2 adsorption-desorption. Experimental factors such as the base source, amount of urea and synthesis duration, which were found to have significant effects on the composition and morphology of the products, were systematically investigated. Gas sensing tests demonstrated the hierarchical flowerlike ZnO with a larger surface area of 51.2 m(2)/g exhibits much higher responses than the ZnO microparticles with a small surface area (15.8 m(2)/g) on detecting analyte gases. (C) 2011 Elsevier B.V. All rights reserved.