We have investigated the influence of light soaking on the electrical and optical properties of sputtered amorphous silicon thin films. The obtained results have shown that sputtered a-Si:H films, as well as glow discharged material are sensitive to prolonged light exposure. The most important induced states appear during the first 21 h of exposure. From the dark conductivity variation, we inferred that light induced defects are relatively low in hydrogen-rich films. We suggest that the mechanism of defect creation is performed through Si-Si weak bonds breaking and that is stabilized by hydrogen involvement. (C) 2002 Elsevier Science B.V. All rights reserved.