The objectives of this study are to provide some rare unfolded grain size distribution data for the sintering of alumina and to test for time invariance of the normalized grain size distribution as required by normal grain growth. The results show that In or doubled during the sintering times studied. The changes in the grain size distribution may be due to an increase in the number of relatively large grains combined with a reduction in the number of grain annihilation events compared with that required for time invariance of the normalized grain size distribution.