Synthesis of metal sulfide semiconductor nanoparticles of group II-VI; namely ZnS, PbS, CdS, and CuS; by mechanochemical method was carried out in a high energy ball mill from corresponding metal acetates and sodium sulfide. The samples were continuously milled for 10 h with sample withdrawal at 2 h time interval. Structural properties of nanoparticles were studied by x-ray diffraction (XRD), transmission electron microscope (TEM), and ultraviolet-visible spectra. Particle size distribution and stability of 10 h milled samples were examined using particle size analyzer and Turbiscan. It was found that nanoparticles synthesized by mechanochemical method had mean particle sizes as small as 2-25 nm, low agglomeration, narrow size distribution, and uniformity of particle structure and morphology.