The effect of small doses of γ‐radiation from 60Co on concentration and mobility of majority carriers in n‐type Si and Ge is investigated. In the oxygen‐containing samples, the mobility is shown to grow anomalously with irradiation dose in the region of combined scattering. A model is proposed which is based on the neutralization of scattering center charges by those of the defects produced by irradiation mainly around the scattering centers. This model qualitatively accounts for the data obtained experimentally.