The effect of low cycle fatigue at 871℃ on the microstructure of Rene´ 80 was studied. The fatigue test was conducted in a push-pull, strain controlled mode with a frequency of 0.05 Hz. The relationship between the plastic strain range and the fatigue life was fitted with the Coffin-Manson model. The alloy showed a cyclic softening initially, which was followed by a steady state until failure. The softening was attributed to a preferrential shearing of secondary γ` precipitates. The dislocation characteristics varied from γ`/γ` localization to γ`/γ` interface misfit dislocations depending on the test condition. A local coarsening of γ` precipitates was also observes. The fatigue crack initiation at surface was accompanied by oxidation, and the mode of crack propagation was predominantly transgranular. The carbides and γ` precipitates were fairly stable against thermal exposures of up to 982℃/70 hrs.