X-ray diffraction technique is one of the most useful method in understanding the exact nature of chemical bonding between metals and ceramics. However, X-ray diffraction at the actual metal-ceramic interface has not yet been performed, though ti has many merits. In this study, the X-ray diffraction at the actual interfaces of six alloy-porcelain composites was performed using a particular method, in addition to the X-ray diffraction of three commercially available precious alloys for porcelain fusing and two commercially available opaque porcelains. The results obtained were summarized as follows: 1) Appreciable reaction layers between alloys and opaque porcelains were not detected. 2) The crystal constituents of two opaque porcelains examined were different considerably. This might affect the metal-ceramic bonding conditions. 3) As for three alloys in this experiments, remarkable differences were not observed in their surface crystal structures after the degassing process.