The purpose of this study was to aid in the prediction of tumor cell tolerance to radiotherapy and/or chemotherapy. For this study, cell surviving curves were obtained for murine melanoma Bl6 cell line using semiautomated M1T assay. 2,4,6,8, 10Gy were irradiated at a dose rate of 210cGy/min using ⁶⁰Co Irradiator ALOORADO 8. After irradiatior, B16 cell lines(2.5×10⁴ cells/ml) were exposed to bleomycin and cisplatin at concentration of 0.2㎍/㎖, 2㎍/㎖ and 20㎍/㎖ for I hour respectively. The viable cells were determined for each radiation dose and/or each concentration of drug. And they were compared to control values. The obtained results were as follows : 1. There was significant difference of surviving fraction at 4, 6, 8, 10Gy on B16 cell line(P<0.05). 2. There was significant difference of cytotoxicity between bleomycin and cisplatin at concentration of 0.2㎍/㎖ and 2㎍/㎖(P<0.05) on B16 cell line, but there was no significant difference of cytotoxicity at concentration of 20㎍/㎖ on B16 cell line. 3. There was significant difference of cytotoxicity of bleomycin after irradiation of 2Gy and 10Gy on B16 cell line(P<0.01). 4. There was significant difference of cytotoxicity of cisplatin at concentration of 20㎍/㎖ after irradiation on B16 cell line.