The effects on the electrical conductivity and the crystalline structure of the addition of HfO2, CeO2, and Ga2O3 to ZrO2 with 11 mol % Sc2O3 (11ScSZ) have been examined. 11ScSZ has the rhombohedral structure and is transformed to cubic structure at 580 degrees C. The cubic phase was stabilized at room temperature by the addition of about 6 mol % CeO2, and 2 mol % Ga2O3 to 11ScSZ. No such effect was observed by addition of HfO2. The electrical conductivity of 11ScSZ was depressed by the addition of HfO2, CeO2, and Ga2O3.