The preparation of beta-sialon from Turkish kaolin by carbothermic reduction under a nitrogen atmosphere has been described. The product of carbonitrothermic reduction at 1475-1500 degrees C comprises principally beta-sialon and minor amounts of another phase in the Si-Al-N-O system known as the 15R phase. The amount of each of these two phases strongly depends on reaction time. The colloidal stability behaviour of the ground carbothermal beta-sialon in water was found to depend strongly on the pH. Slip casting of the beta-sialon powder from the suspension followed by sintering at 1500 to 1600 degrees C resulted in compounds with densities ranging from 94 to 99% of the theoretical value. The particle size of the beta-sialon influences the densification achieved during sintering. The use of yttria in amounts of 5 and 10% as an additive to beta-sialon to obtain higher densities by sintering works well for relatively coarser powder.