Photostructural transformations in amorphous chalcogenide films have been a subject of intensive research so far. In this paper we discuss the changes in the optical properties of typical As-based chalcogenide glasses (As2S3 and As2Se3) on exposure to ultraviolet (UV) light. An attempt has been made to systematically investigate the optical parameters like extinction coefficient, refractive index and optical bandgap of the films by measuring the same for as-grown and UV-exposed amorphous films of As2S3 and As2Se3 prepared by vacuum evaporation technique. (C) 2003 Kluwer Academic Publishers.