Abstract: Objective To evaluate the effect of combined use of oncolytic virus and the chemotherapeutic agents mitomycin(MMC) in growth inhibition of human bladder cancer cell line T-24 in vitro.Methods Human bladder cancer cell line T-24 was infected with oncolytic virus(ONYX-015) of different multiplicity of infection,or treated with MMC in addition to ONYX-015.The changes in the cell growth,morphology,and apoptosis of cultured T-24 cells were observed by means of cell counting and fluorescence microscopy after the treatments.The effects of the treatment protocols were also tested in nude mouse model of implanted subcutaneous tumor.Results Combined use of ONYX-015 and MMC produced substantially stronger cytotoxic effect against T-24 cells than exclusive use of ONYX-015.In in vivo experiments,combination of oncolytic virus and MMC resulted in much more significant tumor growth inhibition than either of the agents used alone.Obvious T-24 cell apoptosis could be observed in response to combined ONYX-105 and MMC treatment and exclusive ONYX-105 treatment.Conclusions ONYX-015 combined with MMC can produce significant cytotoxicity against T-24 cells and enhance therapeutic efficacy against bladder carcinoma.