535.36:548Raleigh and Mandelshtam-Brillouin light scattering has been investigated in chalcogenide glasses of the (As 2 S 3 ) x I 1-x system for x = 1.00-0.80. Longitudinal hypersound velocities, adiabatic elastooptical constants (p 12 ) ad at frequencies of ~15 GHz, and Landau-Placzek ratios R LP are found and scattering losses are calculated. Significant iodine additives are shown to result in the appearance of different features in the behavior of concentration dependences of the investigated parameters.