The origin of the X-ray CTR scattering have been described in brief in order to make it clear why the X-ray CTR scattering measurement can reveal the interface structure. Then, some examples of the results obtained by the X-ray CTR scattering measurement have been shown. The distributions of group-V and III atoms in InP/GaInAs/InP double-heterostructure samples have mainly been discussed. The change of the distribution of As at the interface with the change of H-2-purge time has been quantitatively shown at an atomic scale by the X-ray CTR scattering measurement, which has demonstrated the high resolution and significance of the X-ray CTR scattering measurement in the investigation of the III-V compound semiconductor heterostructures. The distribution of group-III atoms has also been investigated by the X-ray CTR scattering measurement. The results have suggested that the interface has not been so abrupt as expected, and it has been more difficult to control the distributions of group-III atoms than group-V atoms. The results have shown how important the observation by the X-ray CTR scattering has been to understand the interface structure. (c) 2006 Elsevier B.V. All rights reserved.