Nanosized ZnO particles are successfully synthesized via mechanical activation of a zinc nitrate hydroxide hydrate (Zn-5(NO3)(2)(OH)(8)(.)2H(2)O) precursor in NaCl matrix for 15 h. The ZnO particles obtained are in the nanosize range of similar to20 nm, with a well-established hexagonal morphology. They compare favorably with those derived from conventional calcination of the precursor. The decomposition of Zn-5(NO3)(2)(OH)(8)(.)2H(2)O precursor and formation of nanocrystalline ZnO cannot be completed by mechanical activation in the absence of NaCl, which acts as both an effective dispersing matrix and drying agent although it remains chemically inert during mechanical activation. The powder derived from calcination at 400degreesC does not possess powder characteristics comparable to that of the powder derived from the mechanical activation in NaCl, because of the extensive particle coarsening and aggregation at the calcination temperature.