Constant torque torsional creep tests for 3Y-TZP have been conducted in an ambient atmosphere at 1623K to 1773K in the torque range of 0.53 to 1.51Nm. While there are no traces of primary and tertiary creeps, the creep-rate decreases with the increase in strain due to concurrent grain growth. In the shear stress versus shear strain-rate relations obtained in the present experimental range, there exist two regions; one in which m-value is 0.43 to 0.45 and the other in which m-value is 0.21 to 0.22 above and below the shear stress of around 14MPa, respectively. in the former, i.e., high m region, grain size exponent, p similar or equal to 2 and activation energy, Q=443KJ/mol, whereas in the latter, i.e., low m region, p similar or equal to 3 and Q=490KJ/mol. The former region corresponds to the superplastic region II. Regarding the latter region, it seems to be relating to the existence of threshold stress.