Superplastic tensile ductility in Al2O3-10 vol% ZrO2 (3 mol% Y2O3) exhibits processing dependence when the grain size is reduced to 0.45 mum for a given relative density of similar to99.5%. The reduced grain size leads to largely enhanced ductility in a material prepared by. colloidal processing, but does not in a material prepared by conventional dry processing. This result is explained from cavity-damage accumulation sensitive to a rather small variation in a few processing-dependent factors: the numerical densities of residual defects and ZrO2 particles. The rate of damage accumulation is shown to depend mainly on the former and additionally on the latter.