Fatigue-crack growth rate tests were conducted at 427°C on lrradiated 600, Inconel X-750, and Incoloy 800 irradiated in the Experimental Breeder Reactor II to total fluences ranging between 2.5 and 6.0 X 1022 n/cm2. Following irradiation, minor increases were noted in the crack growth rates of Inconel 600, minor decreases in the growth rates of Inconel X-750, and no irradiation effect in the cracking behavior of Incoloy 800.