The unaltered incidence of recurrence of superficial bladder tumor after discontinuation of intravesical chemotherapy has prompted a search for effective adjuvant therapy. The technique of cauterization and implantation of tumor cells was performed in C3H/He mice to simulate the early stage of bladder cancer to evaluate a regimen of intravesical mitomycin C followed by the systemic immunopotentiator, levamisole. Mice received either normal saline (control), mitomycin C (MMC), levamisole (Leva), or MMC plus Leva. Chemotherapy was given intravesically on days 6 and 13. Immunotherapy was given intraperitoneally on days 7 and 14. All mice were sacrificed on day 21. In the treatment groups, the incidences of bladder tumor varied from 50 to 63 per cent whereas that of the control group was 91 per cent. An increase in spleen weight was observed in the treatment groups of Leva and MMC plus Leva as well as the control group but not observed in the group receiving MMC. Our study suggests that although Leva did not reduce the tumor incidence, an immunostimulator might be of benefit when used in conjunction with MMC.