We have investigated the structural and chemical stability of La 0.8Sr 0.2MnO 3 (LSM)-8mol.% yttria stabilized zirconia (YSZ) composite. LSM and YSZ powders were mixed and sintered at 1400°C for 10h in controlled atmosphere (PO 2=0.21 to 10 -6atm). The unit cell volume of LSM increases during exposure to reduced oxygen partial pressure while it remains unchanged for YSZ. During reduction in the oxygen partial pressure from 0.21atm to 10 -6atm, the solubility of manganese in YSZ increases from ~10at.% to ~15at.%. Lower oxygen partial pressure also results in the grain growth and formation of La 2Zr 2O 7 and MnO x (Mn 3O 4) compounds lowering the stability of the LSM-YSZ composite. On subsequent sintering in 0.21atm PO 2, the La 2Zr 2O 7 and MnO x compounds tend to disappear indicating the reversibility of the interaction. The reversibility of LSM-YSZ reaction has been independently confirmed using La 2Zr 2O 7 and MnO x. © 2012 Elsevier Ltd.