Uniaxial fatigue properties from tests at 400, 500, 600, and 700 C on Type 304, 304L (Ti modified), and 316 stainless steel specimens irradiated at 450 C in sodium and 750 C in argon at fluences of 0.03 to 9.3×10²¹ n/cm², E>0.1 MeV, are given and compared with control specimens. Material was tested in the annealed, cold-worked, and chilled-swaged-tempered condition, while primary controls received a pretest anneal of 1500 h at 750 C. The data at 400, 500, and 600 C are compared with proposed design curves for 18-8 steels. Some data on microstructural changes due to irradiation are given. A reduction in the fatigue life by a factor of less than 2.5 was found in the annealed material, which was attributed to irradiation damage. A beneficial effect on fatigue life of pretreatment by swaging was found after irradiation at 450 and 750 C for 2550 h.