Amorphous powders of Al2O3-37.5 mol% Y2O3 (yttrium aluminum garnet (YAG)) were prepared by coprecipitation, decomposed at 800 degrees C, and hot-pressed uniaxally at low temperature (600 degrees C) and a moderate pressure (750 MPa). Optimum conditions yielded microstructures with only 2% porosity and partial crystallization of YAG. Further processing using high quasi-hydrostatic pressure (1 GPa) at 1000 degrees C enabled the production of fully crystallized YAG with > 96% relative density and a nanocrystalline grain size of similar to 70 nm.