The irreversible and reversible photoinduced changes of the structure and physical properties of stoichiometric and non-stoichiometric AsxS100-x, (x = 38, 40) thin films were studied. The changes in intensities of Raman bands were interpreted in terms of changes of short-range order. The illumination and/or annealing of fresh-evaporated As-S system thin films change the As4S4 and S-n contents as well as the densities of As-As and S-S bonds. Illumination and annealing shift the short wavelength absorption edge towards lower energies and changes the index of refraction. The energy dependence of the index of refraction, n, can be described by the Wemple-DiDomenico dispersion relationship n(2)((h) over bar omega) - 1 = EoEd/[E-o(2) - ((h) over bar omega)(2)], from which the single oscillator energy, E-o and the dispersion energy, E-d, were determined. The dependence of E-o, E-d, n, and of the thickness of the sample d on the stoichiometry, illumination and annealing are also discussed.