Magnesium hydroxide (Mg(OH)(2)) nanoflowers of uniform morphology and size have been prepared by a simple hydrothermal reaction of MgCl2 and CO(NH2)(2), Without any organic additive or catalyst. Several petals are observed to self-assemble within a single flower grown on smaller crystal nuclei, while each petal with a thickness of about one hundred nanometers exhibits a specific morphology. Spherical particles with smooth surfaces are those composed of individual nanosheets can be successfully obtained by adjusting the pH values of the initial reaction solution. The influence of temperature on the formation of Mg(OH)(2) nanoflowers has been found as well. (c) 2005 Elsevier B.V. All rights reserved.