We report IR and Raman spectra obtained on a highly ion-conducting glass-forming system, x(AgI)(2).(1 - x)Ag2SeO4 with x = 0.35, 0.40, 0.46, 0.48, 0.50, 0.54. For 0.48(AgI)(2). 0.52Ag(2)SeO(4), spectra were recorded in a temperature range between room temperature and 573 K, probing the glassy, partly crystallized, and molten slates of the material. The spectra of the glasses are compared with those of the crystalline compounds Ag2SeO4 and alpha-AgI. Conclusions reached from the present work are consistent with those recently derived from neutron diffraction and dynamic conductivity measurements on the same materials.