[en] Unirradiated Vanstar-7 alloy was tested in fatigue at room temperature, 550⁰, and 650⁰C, respectively, in high vacuum below 10/sup -5/ Pa. The test data are analyzed and compared with those of V-15Cr-5Ti and 20% cold-worked type 316 stainless steel tested under the same condition. Results show that the fatigue resistance of Vanstar-7 is in general somewhat lower than that of V-15Cr-5Ti. The low fatigue performance for Vanstar-7 at the elevated temperatures in the high cycle range may be attributable to thermal creep damages because Vanstar-7 is less creep resistant than V-15Cr-5Ti. However, Vanstar-7 exhibits superior fatigue resistance compared with the stainless steel in the low strain range below 0.5% strain