Interfacial reactions in four kinds of diffusion couples, Pt/Ti, Pt/Zr, Pt/TiO2, and Pt/ZrO2, are examined. Ti3Pt, TiPt, and gamma phases are observed in the Pt/Ti couples annealed at 800 degrees C. PtZr and Pt3Zr5 are formed in the Pt/Zr couples reacted at 900 degrees C. No noticeable reaction are found when TiO2 and ZrO2 are annealed in contact with Pt with relatively high oxygen activities.