High-temperature tensile tests were repeatedly carried out for a tetragonal zirconia polycrystals (TZP) specimen, and the position vectors of 500 grains were measured by FE-SEM image analysis. The displacement vector map showed that several grains moved to the same direction and a kind of domain was formed; these domains (several micrometer in size) moved in the sea of randomly moving grains; however, these domains were soon constrained by the surrounding sea and disappeared; subsequently, new domains were formed in other places by re-combillation of grains in order to continue superplastic deformation. Based on these phenomena, the authors proposed a new deformation mechanism called '' Recombinant Domain Movement '' in this paper. (c) 2005 Elsevier B.V. All rights reserved.