Hysteresis loop measurements were conducted on several commercial iron‐nickel alloys during neutron irradiations at 90°K and at temperatures up to 175°C, in both zero and saturating magnetic fields. Isochronal annealing tests were also performed on the alloys after irradiation. The low‐temperature irradiation results indicated that magnetic properties are affected not by the point defects themselves but by their motion and eventual disposition. The radiation‐induced changes appeared similar in many ways to those observed in these alloys upon magnetic annealing.Experiments on the alloys at temperatures from 70° to 175°C in a saturating magnetic field showed that the activation energy of the radiation‐induced process was 0.3 eV. In all cases the radiation‐induced changes were annealed out at temperatures below the usual ordering temperature for Ni3Fe. This recovery process appeared to be dependent upon the state of the magnetization of the sample.