Considered as an electrode for SOFC, the system Gd 1 - x Sr x CoO 3 was studied for the electrical conductivity, cathodic polarization and reactivity between Gd 1 - x Sr x CoO 3 and YSZ (8 mol% Y 2 O 3 doped zirconia). Although the cathodic activity is excellent and similar to the La 1 - x Sr x CoO 3 system, the formation of SrZrO 3 at the interface between Gd 1 - x Sr x CoO 3 and YSZ was observed at higher temperature, which causes the deterioration of the cathodic activity. However, GdCoO 3 , being different from LaCoO 3 , yields no reaction product with YSZ at high temperature and shows no deterioration in the cathodic activity for the electrode even when sintered at 1000 o C.