Intraluminal hyperthermia is potentially useful in the management of superficial bladder cancer. The potential inhibitory effect of hyperthermia on various human bladder cancer cell lines, normal human bladder cells and the murine MBT-2 bladder cancer cell line has been studied in vitro. These cell lines were exposed for one hour to 43 +/- 0.5C and compared to controls. Cell survival was assessed comparing the cell growth curve and colony formation. The human transitional cell carcinoma (TCC) cell lines vary in their sensitivity to heat. MGH-U1 was the most heat sensitive cell line. The human A-1698, CUB-2, UM-UC-3 and the murine MBT-2 lines were heat insensitive. We conclude that the cytocidal effect of hyperthermia in bladder transitional cell carcinoma is variable. Further experiments using the combination of hyperthermia and intravesical anticancer agents are in progress.