The effect of nanocrystalline leucite seeding with leucite precursors prepared by sol-gel and hydrothermal methods on the leucite crystallization process and the microstructure of its sintered porcelain was studied. The introduced seeds lowered the crystallization temperature of leucite by 100 degrees and 50 degrees C for the precursor prepared by hydrothermal and sol-gel methods, respectively. The crystallization process was changed after the seeds were introduced. As the transition phase during leucite crystallization, kalsilite did not appear after the seeds were added. When the seeded hydrothermally derived precursor was treated at 650 degrees and 700 degrees C, part of the cubic leucite was stabilized to room temperature. This stabilization was due to the crystallization of nanocrystalline leucite on the seeds at a low temperature. The leucite synthesized by the hydrothermal method with seeding at 800 degrees C had an average particle size of 0.4 mu m that grew to about 0.6 mu m in the sintered porcelain.