Depending on the duration of exposure to supraphysiological temperatures, cellular proteins and organelles can suffer from structural alternations and irreversible denaturation, which may induce cell death. The thermotolerance of three human urinary bladder carcinoma cell lines, TSGH-8301, J82 and TCC-SUP (cytological grade 2, 3 and 4, respectively), was investigated in the present study. A home-made heating stage was used to provide a constant temperature for different cell lines of bladder carcinoma. The experimental data showed that the TCC-SUP and TSGH-8301 cells exhibited the lowest and highest thermotolerances, respectively, while J82 cells were intermediate. Moreover, the differences in the thermotolerances for the TSGH-8301 and J82 cells are significant when the supraphysiological temperature is higher than 43 degrees C. As for TSGH-8301 and TCC-SUP cells, the thermotolerances are significantly different for all of the thermal treatments tested. Furthermore, the thermotolerances of J82 and TCC-SUP are significantly different when the cells are exposed to a temperature less than 50 degrees C for longer than 2 min. Overall, the results suggest that the high cytological grade of the cell line of bladder cancer exhibits a low thermotolerance. The kinematic parameters of the activation energy and frequency factor for bladder cancer cell lines with different cytological grades were also quantitatively evaluated in this work.