It has been shown that the &ggr;‐radiation‐induced hardening of NaCl is strongly dependent on temperature [between liquid‐nitrogen temperature (LNT) and room temperature (RT)] for low irradiation doses, but it is essentially independent of it for doses ≳6×106R. For very low doses ≲1×106R the experimental data can be analyzed in terms of a rapid solution hardening mechanism of the type proposed by Fleischer. For higher doses this model is not adequate and one should think of a precipitation (Orowan) hardening mechanism.