High-quality polycrystalline ZnS grown by Chemical vapor deposition (CVD) method and their optical properties are reported in this paper. The particular CVD furnace of reasonable structure was designed and fabricated domestically. A technique directly using solid Zn and S as raw materials was adopted. For the purpose of obviating the pollution to environment, H2S for growing crystals is produced in a homemade gas-producing equipment, which is placed inside the furnace. Growth parameters such as temperature, pressure and gas flow are optimized. Optical polycrystals of CVD ZnS are slightly yellow in color, transparent, homogeneous and bubble free. The size of the grown bulk CVD ZnS is up to 200 mm in diameter and 10 mm in thickness or 300 mm in length, 250 mm in width and 8 mm in thickness. For 4 mm-thick polycrystals of ZnS, the average transmittance is about 75% for the wavelength range from 8 to 10 mus, which is near to the theoretical transmittance of the material. (C) 2002 Elsevier Science B.V. All rights reserved.