An X37CrMoV5.1KU hot working steel was quenched and tempered, nitrided, overcarburised, overcarburised and nitrided, and nitrocarburised for 18 and 36 h. Wear tests at 50 and 100 kg loads were performed without lubricant on the treated specimens using an A135 Amsler machine in order to determine the most effective treatment. The quenched and tempered specimens showed the worst behaviour and the nitrocarburised specimens the best. Nitriding performed without or after overcarburising on the specimens tested at the lowest load appreciably increased wear resistance, while minor benefits resulted from overcarburising. For the specimens tested at high loads the benefits of nitriding after overcarburising remained, while the behaviour of nitrided or overcarburised specimens was similar. The wear resistance of the treated specimens was related to surface layer characteristics and in particular to the presence of intergranular precipitates.