The effects of collection geometry, vapor cooling, gas pressure, and the nature of the inert gas have been investigated with respect to particle size, morphology, and microstructure of ZnS nanocrystalline powders prepared by the gas-phase condensation method. The materials have been characterized by transmission electron microscopy, X-ray diffraction, and UV-vis absorption spectroscopy. It has been found that adequate control of the experimental conditions can produce powders of controlled mean particle size and morphology. This tailored nanocrystalline microstructure also determines the electronic characteristics of the materials, in particular, band gap absorption values.