Thin films of SnS have been prepared by electron beam evaporation. The films represent Herzbergite orthorhombic structure, established by their XRD patterns. The band gap energy and type of optical transitions were determined from transmission spectra and an optical band gap of E-g(tr) = 1.23 eV for indirect transitions and E-g(tr) = 1.38 eV for direct transitions were estimated. Using the dependence of photoconductivity from wavelength, a band gap of E-g(ph) = 1.2 eV was determined as well. A thermal band gap of E-g(T) = 1.29 eV was evaluated from the temperature dependence of the dark resistivity, and admixture level with activation energies (0.25 and 0.36 eV) were found. Roughness of the surface of SnS thin films was evaluated using atomic force microscopy. (C) 2003 Published by Elsevier B.V.