Single-phase small crystals of Li-, Mg-, Ca-, Y-, Nd-, and Yb-alpha-SiAlONs have been obtained by liquid-phase sintering for various compositions and processing conditions. These crystals are suitable for seeding grain growth in alpha-SiAlON ceramics. The influence of chemical and processing parameters (starting composition and powders, green density, liquid content, heating schedule, nitrogen pressure, and temperature) on the size and morphology of seed crystals has been investigated. The results are compared with those for beta-Si3N4 crystal formation, and the differences are discussed in terms of nucleation and growth kinetics during liquid-phase sintering.