We determined the increase of the electrical resistivity in copper, Be doped copper, and in gold during irradiation with 1.85 MeV electrons below the temperature corresponding to the stage III recovery region. From the analysis of these data by means of rate equations we are able to determine the variations of the concentrations of interstitials, vacancies and agglomerates of interstitials as a function of the irradiation time and of the irradiation temperature.