The optical transmittance and reflectance of SbSI single crystals had been measured for photon energies from 1.5 to 2.6 eV in temperature range from 77 K to 343 K. The experimental data had been evaluated to determine anisotropic, spectral and temperature dependences of real part of refractive index and absorption coefficient of SbSI. The temperature dependence of the energy gap had been evaluated from the spectral characteristics of absorption of light with electric field parallel and perpendicular to the c axis of the SbSI. The phase transition had been determined from the temperature dependences of optical parameters as well as from the temperature dependence of the energy gap. The photoconductivity of the investigated crystals had been measured as a function of photon energy, illumination intensity and temperature.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.