The master’s thesis deals with the problem of the injection mould wear in the process of injecting glass reinforced polymer. The thesis presents a detailed analysis of literature upon which the experimental part is based, where the wear resistance of four cavity inserts of various heat treatments and materials is considered. The work is based upon assumption of a different degree of wear in individual cavity zones. The experimental part was performed on a prototype injection mould in which the said cavity inserts were installed. The test involved 10 000 shots of PA66 GF35 thermoplastic material. Wear rates are quantified with Ra and Rz roughness parameters before and after the experiment was conducted. Optical microscopy and interferometry were also used to observe present wearing mechanisms. The highest wear rate was detected in the region of the tunnel gates of the cavity inserts, which is reflected in the distortion of their geometry. Different wear durability was detected at different materials and heat treatments.