beta-In2S3 in powder form was chemically synthesized using InCl3 and thioacetamide as precursors followed by annealing in argon atmosphere in the temperature range 573-1123 K. The composition of the powder was determined by XRF. X-ray diffractornetry showed the beta-In2S3 phase to retain a tetragonal structure throughout the range of annealing temperature. Microstructural investigation with scanning electron microscopy indicated the particle size to vary from 0.40 to 1.48 mum. Optical band gap of the powder was determined from the reflectance studies as a function of wavelength and was found to be similar to2.12 eV. Photoluminescence studies indicated a strong peak around 2.08 eV for all the samples annealed (argon) in the range similar to573-1123 K. (C) 2003 Elsevier B.V. All rights reserved.