During laser machining of ceramics, cracks can occur in the material around the irradiated area. These cracks reduce the strength of machined parts and may possibly hinder their use as an engineering material. It is therefore very important to establish methods for the detection and avoidance of crack formation. As an aid for detecting crack formation, the acoustic emission method was used for two materials: soda lime glass and sialon. The results have led to the conclusion that it is possible to detect a signal coming from a crack in the investigated material and that the power of the detected signal is due to propagation of the crack. The relationship between laser parameters and crack formation was found with the aid of acoustic emission signal analysis. It was also found that it is possible to minimise or avoid crack formation by choosing suitable laser parameters