We give a theoretical estimate of the lower limit of Rayleigh scattering in sapphire crystals. We report measurements of scattering attenuation coefficient in sapphire at wavelengths of 633 and 1064 nm using an imaging measurement technique. The measured scattering loss in sapphire is similar to 13 ppm/cm. Using sapphire as a mirror and beamsplitter substrate in laser interferometric gravitational-wave detectors, Rayleigh scattering losses are similar in magnitude to estimates of mirror losses. However, the scattering level still remains higher than the theoretical limit because of the presence of impurities vacancies in the sapphire crystal. (C) 1999 Published by Elsevier Science B.V. All rights reserved.