To explore the possibility to employ 99m Tc MIBI to monitor biological response of tumor cells after irradiation and to observe the relation between the radiation doses and the uptake levels of 99m Tc MIBI in tumor cells, the cells were irradiated with a single dose of 2 Gy, 10 Gy and 20 Gy respectively. The uptake of 99m Tc MIBI in each dosage group was determined before and 24, 48, 72 h after irradiation respectively. Apoptosis index , plating efficiency of tumor cells was simultaneously determined. There was a positive correlation between uptake levels of 99m Tc MIBI and AI. A negative correlation was noted between the uptake levels and PE . It is suggested that 99m Tc MIBI may be used as a tracer to monitor the change of viability state of tumor cells after being irradiated with different doses. To explore the possibility to employ 99m Tc MIBI to monitor biological response of tumor cells after irradiation and to observe the relation between the radiation doses and the uptake levels of 99m Tc MIBI in tumor cells, the cells were irradiated with a single dose of 2 Gy , 10 Gy and 20 Gy respectively. The uptake of 99m Tc MIBI in separate dosage group was determined before and 24, 48, 72 h after summer respectively. Apoptosis index , plating efficiency was tumor cells was not determined. Uptake levels of 99m Tc MIBI and AI. A negative correlation was noted between the uptake levels and PE . It is that suggested 99m Tc MIBI may be used as a tracer to monitor the change of viability state of tumor cells after being irradiated with different doses .