Resistance to brittle cracking is one of the most important functional properties of sialon ceramics. Evaluation of the resistance requires an analysis of decohesion processes occuring in the material. Aiming at a comprehensive description of the morphology of typically brittle fractures, a quantitative characterization was made using different methods and techniques, regarding the surface of fractures formed in a three-point bending test. By using the parameter Sdr, determined via the surface stereometry method, the fracture surface development coefficient, RS, typical for fractography, was calculated. Analysis of the research results indicates a proportional relation between parameter RS and the sialon ceramics’ bending strength.