In an attempt to elucidate some aspects of the radiobiological basis of targeted radiotherapy in oncology,the apoptosis occurred have been studied in Hela cell lines after exposing to different doses and dose—rate radiation of ,32,P and the relationship between apoptosis occurred and the capacity of cell proliferation,which might be of help to the understanding of targeted radiotherapy. Asynchronous Hela cells were exposed to ,β, radiation from ,32,P absorbed in filter papers which were put closely under culture dishes of growing monolayer of Hela cells. The radiation response characteristics to different dose、dose—rate and radiation time were evaluated through cell—proliferation assessed by the colony—forming assay, cell cycle perturbation studied by flow cytometry and quantity analysis of apoptosis analyzed by flow cytometry and fluorescence microscopy. Morphological and flow cytometry analysis showed a delayed apoptosis. The programmed cell death approached a plateau between 48—72h post—irradiation. Electron and fluorescence microscopic studies showed the presence of morphologically apoptotic cells. Single dose radiation showed a higher apoptosis ratio than multiple low dose radiation, which didn't correlate with clonal—forming assay,suggesting apoptosis ratio at a near time point post—irradiation is not a convincing indicator of radiation efficacy in the current experimental setting.