The comet assay (single cell gel electrophoresis assay) was used to evaluate the radiotoxicity of Auger electron emitters in the human osteosarcoma cell line (HOS-8603). After internal exposure to ⁶⁷Ga-EDTMP, the sarcoma cell has been injured severely. The comet length was longer along with the increase of dose, the appearance of comet tail was different from that with respect to the ⁶⁰Co γ-ray irradiation. DNA damage of cell was mainly due to the radiation effect of Auger electrons. The ⁶⁷Ga may be a therapeutic radionuclide with good prospect for tumor treatment and palliation of bone pain induced by metastasis.