The crystal structure of high-temperature Cr (III) 0C1 is kno.wn but nevertheless there exist no previously published X-ray diffraction data suitable for routine Identifi¬cation purposes. In the present work Cr (III) OC1 was prepared free from crystalline Cr2O3 at the relatively low temperature of 590°C by reacting dried chromic hydrate with anhydrous CrCI3. Low-temperature samples of Cr (III) OC1 prepared using low-temperature and high temperature CrCl3 were examined with a Guinier camera. The X-ray powder diffraction pattern of the former sample of Cr (III) OC1 was also indexed in the range 20—10-63° with a diffractometer. The three strongest lines observed were 7.67 dA (100 I /Io), 3.441 (100) and 2.441 (60). The X-ray powder diffraction data obtained, along with previously unpublished reference data for high-teperature Cr (III) OC1, are tabulated in a form suitable for ro¬utine Identification purposes