Abstract The interrupted creep tests (ε=0.1%) of a fourth and a sixth generation Ni-base single crystals, i.e. MX-4/PWA 1497 and TMS-238, were conducted at 800°C and 735MPa along . TMS-238 had a creep time more than sixty times longer than MX-4/PWA 1497. Microstructural observations showed that stacking faults (SFs) sheared both the γ matrix and γ΄ precipitates in MX-4/PWA 1497, however, SFs sheared only the γ matrix in TMS-238. The factors that affect the creep deformation are discussed. The results imply that the stacking fault energy (SFE) of γ matrix in TMS-238 is lower than that in MX-4. Higher additions of Re and Ru are responsible for the lower SFE in TMS-238.