The Raman spectra of barium peroxide (BaO2) in the O-O stretching region were studied at various temperatures between 22 and 850 degrees C in both O-2 and He atmospheres. Although only one peroxide stretching band is expected for the crystal symmetry, three Raman bands, which were assigned to peroxide ions in different crystal environments due to the relative locations of oxide impurities, were observed at all temperatures. The temperature dependencies of the Raman frequencies, bandwidths, and the absolute and partial intensities were investigated in detail, and these were explained on the basis of the sample composition and structural changes.