The oxidation resistance of beta-Sialon processed with Y2O3 sintering additive and beta-Sialon/TiN composites containing 1-10 wt% TiN was studied using ion beam analysis (IBA) techniques, augmented by XRD and SEM measurements. Rutherford backscattering spectrometry was used to monitor the diffusion of Y and Ti in the oxidised samples, and the diffusion of oxygen and nitrogen was observed by particle-induced gamma emission and nuclear reaction analysis. These techniques showed that in the Sialon control sample without TiN, oxygen was the first element to migrate at 1000 degrees C, followed by Y and N at 1100 degrees C. At 1200 degrees C, a N-poor, Y- and O-rich oxidised layer was formed, containing crystalline Y2Si2O7. In the TiN-containing samples, Si, Al, Y and Ti were very mobile even at 1000 degrees C and the surface nitrogen was depleted by 1250 degrees C. The combined presence of yttrium aluminium garnet (YAG) and TiN protects the piSialon phase by forming an oxygen-rich crystalline barrier layer. The oxidation products of TiN in these composites are TiO2 and Y2Si2O7 , The details of the oxidation mechanism of the (beta-Sialon/TiN composites provided by these IBA studies (movement of yttrium and titanium, replacement of nitrogen by oxygen in the glassy yttrium phase and major crystalline and chemical changes in an outer oxidised layer) could not readily have been obtained by any other techniques, and illustrate the value of IBA for oxidation studies of non-oxide ceramics.