Chemical-bath deposition of ZnS thin films from NH3/NH2-NH2/SC(NH2)2/ZnSO4 solutions has been studied. The effect of various process parameters on the growth and the film quality is presented. A first approach to a mechanistic interpretation of the chemical process is reported. The structural, optical, chemical, and electrical properties of the ZnS thin films deposited by this method have been studied. The electron diffraction (EDS) analysis shows that the films are microcrystalline with a cubic structure. EDS analysis has demonstrated that the films are highly stoichiometric. Scanning electron microscopy studies of the ZnS thin films deposited by this method show that the films are continuous and homogeneous. Electrical conductivity measurements have shown the highly resistivity nature of these films (sigma = 10(-9) S cm-1).