Preliminary data relating to the fatigue life and fracture morphology of an austenitic stainless steel at temperatures of 475 and 745 C are presented. From metallographic examination, fracture at 475 C was seen to be transcrystalline and ductile in nature, while at 745 C it appears that grain boundary cavities formed and subsequently linked up to give a mixed intercrystalline-transcrystalline fracture, the proportion of each depending on the level of the applied stress; fractographic examination supports these observations. Many grain boundary carbides were present on the intercrystalline fracture surfaces formed at 745 C, and the role of these in initiating crack formation is considered worthy of further study.