The effect of initial density and rapid prestraining on superplastic ductility of 1 wt-%CuO doped cubic zirconia (8Y - CSZ) was investigated, To obtain a range of initial densities, the tensile test specimens were slip cast to net shape and pressureless sintered over a range of temperatures in air. The specimens were then superplastically tested at a temperature of 1500 K and at a constant strain rate of 1 x 10(-4) s(-1). The results showed that specimens with low initial densities had lower flow stresses and higher superplastic elongations to failure than higher density specimens. The reasons for the ductility change were discussed with reference to the presence of porosity and grain growth, For the prestraining test, a specimen with an initial density of 95% was prestrained to 30%, at a temperature of 1550 K and at a prestrain rate epsilon (1) of 1 x 10(-3) s(-1), followed by elongation to failure at a slower test strain rate epsilon (2) of 1 x 10(-4) s(-1). It was seen that prestraining at the above test conditions considerably improved superplastic ductility, The reasons for this ductility enhancement were explained in terms of suppression of grain growth. MST/4602.