Single-crystalline zinc oxide (ZnO) with needle-like and flower-like morphologies has been successfully synthesized by decomposition of Zn(OH)(4)(2-) in aqueous solution at 90degreesC. The reaction temperature, reaction time, and zinc source are important factors in determining the phase and morphology of ZnO. When using zinc acetate as the zinc source at 90degreesC for 90 min in an oil bath, ZnO with the needle-like morphology was obtained. Whereas using zinc nitrate as the zinc source, ZnO with flower-like morphology was produced.