Interfacial reaction between yttria-stabilized zirconia (YSZ) and La0.6Sr0.4MnO3 (LSM) phases was analyzed by X-ray diffraction and high-resolution transmission electron microscopy. The interface was basically constructed by binding of well-crystallized grains even in the vicinity of the interface. The interfacial reaction was observed typically for the sample heated at 1500 degrees C. Amorphous regions were partially formed by solid-state reaction between LSM and YSZ particles. Some small crystallites which had lattice orientation different from neighbouring LSM and YSZ particles near the amorphous phase were observed, and were attributed to lanthanum-zirconate and strontium-zirconate phases.