The microstructural properties and wear behaviour of AISI H13 steel which had been plasma nitrided at 530 and 550-degrees-C for times between 4 and 100 h have been investigated. The effect of treatment temperature and time on the microstructure have been examined. The wear behaviour of material treated for 4 and 100 h has also been observed. It was seen that a total case depth of 0.55 mm with a hardness of 1000 HV can be achieved in 100 h. However, the white layer thickness is increased to 17-mu-m while the core hardness is reduced to 480 HV at 550-degrees-C. The wear rate of the sample treated at 550-degrees-C for 100 h is higher than that of the sample treated at 550-degrees-C for 4 h.