The sintering and grain size of sub-micrometric CeO2 and ZrO2 + 3 mol%Y2O3 prepared by injection moulding and cold isostatic pressing were studied. Using combinations of the ceramic powders used and shaping methods, three types of bodies were prepared that were characteristic by their own green body microstructure. Their sintering behaviour was described with the aid of high-temperature dilatometry. Each type of specimen was then sintered to two levels of final density (higher than 98% t.d.), for each density always via two or three different firing modes differing in temperature and holding time. In the ZrO2 specimen it was verified statistically that the final grain size was the same irrespective of whether the given final density was obtained by sintering for a longer period at a lower temperature or for a shorter period at a higher temperature. This finding did not hold for the injection moulded CeO2 cylinders, which contained cavities in the order of millimetre. When these defects in the structure of CeO2 ceramic were removed, it was verified statistically also for this material that the final grain size was a function of the density obtained and not the temperature cycle with which this density was obtained.(c) 2005 Springer Science+ Business Media, Inc.