Abstract: Objective :To study the growth suppression and induced apoptosis combined effect of 4-HPR and y-radiation on transitional cancer cells of human bladder and to analyze whether there would be synergistic action between them. Methods :MTT calorimetric assay was employed to examine the growth status of the cells. Flow cytometer was employed to detect the growth inhibition effect of 4HPR and/or y-radiation on bladder cancer cell line T24. Results :te were 0.3%, 12.5% and 26.7%, respectively. In the group of treatment with 2.SN.,mo1/L or SN.,mol/L 4-HPR and 100cgy y-radiation, on day 3 the apoptosis ratio were 20.0% and 26.0%, and the average mortality rate of cells were below 5.0%; whereas on day 5 the apoptosis ratio were 38.0% and 35.0%, and the mortality rate were 12.4% and 21.1% respectively. Conclusions :The apoptosis ratio of 2.SN.,mo1/L,SN.,mol/L and lON.,mol/L 4-HPR-reated T24 cells on day 5 were 6.2%,28.0% and 26.0%,and the mortality raConclusion: Micro-dosage 4-HPR may induce T24 cells apoptosis, where maximus dosage 4-HPR may induce cell death. Micro-dosage 4-HPR combined with Micro-dosage γ-radiation have the synergistic action on T24 cells apoptosis.