A phase transition occurring at 320 K in DCrO 2 but not in HCrO 2 has been investigated by infrared spectroscopy. The hydrogen bond bending vibration is sensitive to the phase transition, the peak frequency changing sharply with temperature at the transition temperature. The Cr-O vibration region is also sensitive to temperature. The absorption peak occurring at 434 cm− 1 for DCrO 2 .below 320 K has been examined closely with respect to the intensity and band width. Dispersion-like anomalies in the spectra (the Evans-Fano effect) have been studied by analysis of the spectral shape function.