Self-assembled zinc sulfide nanoballs were prepared in saturated aqueous solutions via a microwave-assisted route. Zinc acetate and thioacetamide were selected as zinc source and sulfur source, respectively. Powder X-ray diffraction, transmission electron microscopy, selected area electron diffraction, X-ray photoelectron spectra, Fourier transform infrared and Thermogravimetric analysis were used to characterize the as-prepared products and the optical properties was studied by diffuse reflection spectra and photoluminescence spectra. Zinc sulfate and zinc nitrite can also used to prepare ZnS nanoparticles instead of nanoballs. The mechanism for the assembly of ZnS nanoballs was also discussed. (C) 2004 Elsevier B.V. All rights reserved.