© 2015 The Ceramic Society of Japan. The regenerability and stability of lanthanum strontium manganite (LSM)/yttria doped zirconia (YSZ)/LSM symmetrical cells have been examined after the cells were exposed to real-world air environment containing H2O and CO2. An alternate exposure experiment in 20% H2O-air and dry air has been conducted to test the reversibility of the cell degradation in H2O/air. Long-term experiment in 3% H2O-0.5% CO2-air, dry air, 0.5% CO2-air, and 10% CO2-air has shown the stability and regenerability of the cell performance. Additional experiments show that periodic water content fluctuation causes the cell performance fluctuation. Electrochemical performance measurements and post-test microstructure analysis indicate that the segregation of SrO on the LSM surface and formation of La2Zr2O7 at the LSM/YSZ interface degraded the electrochemical performance by increasing the polarization resistance. The cell performance degradation can be partially recovered by exposure to dry air. Thermogravimetric analysis (TGA) has been conducted for the LSM as well as its constituent oxides to elucidate degradation mechanisms. Mechanisms related to the performance degradation and regenerability have been proposed.