To study radiosensitizing effect and apoptosis induction of tamoxifen on human glioma cells, 3,H-TdR incorporation assay, flow cytometry, laser confocal microscope and Immunohistochemistry were used to investigate the inhibition effect on DNA synthesis, apoptosis and estrogen receptor expression. Experiment results suggested that tamoxifen could inhibit DNA synthesis in SHG-44 cells,the combination of tamoxifen and ,60,Co γ-irradiation showed a synergistic action on it. Tamoxifen could also induce the apoptosis, and the apoptosis rate increased along with tamoxifen concentration was elevated, so morphologyical changes, such as karyopyknosis, nuclear fragmentation and apoptotic body were observed. However, SHG-44 cells did not express estrogen receptor. The above results revealed that tamoxifen can sensitize SHG-44 cells to gama radiation, which might be related with apoptosis pathway instead of the estrogen receptor-mediated process.