In order to investigate the effects of TiC and Cr₂₃C₆ carbides on creep-fatigue behaviors, total strain range controlled creep-fatigue tests of TiC and Cr₂₃C₆ aged AISI 321 stainless steels with the same carbide density at the grain boundary were conducted at 600°C. It is observed that creep-fatigue life of TiC aged alloy is longer than that of Cr₂₃C₆ aged alloy in the same test conditions. To verify the origin of the difference in creep-fatigue life between the two alloys, microstructural observations are conducted by scanning electron microscope (SEM) and transmission electron microscope (TEM). It is understood to be due to the strong cavitation resistance of TiC aged alloy compared with that of Cr₂₃C₆ aged alloy. It is considered that formation and growth of cavities are retarded by strong interfacial affinity between TiC and matrix.