High-strain-rate superplasticity (HSRS) of ZrO2-30vol% MgAl2O4 spinel composite was examined. The general trend of the stress-strain rate relationship can be characterized by a strain rate sensitivity of m approximate to 0.5. The flow behavior can be ascribed to grain boundary sliding (GBS). The experimental results suggest that HSRS can be attained by an enhanced accommodation of stress concentrations exerted by GBS through the deformable spinel particles.