Abstract: Objective To study the effect of oncolytic adenoviral Ad-MK alone or combined with or without irradiation on human transitional cell carcinoma cells EJ. Methods RT-PCR was employed to detect midkine and Adenovirus E1a mRNA expression in EJ cells after infection with Ad-MK.The survival rations of the cells were performed by MTT.The effect of Ad-MK combined with radiation was performed by survival fraction.Virus yield of Ad-MK was determined by TCID50. Results The midkine mRNA and E1a mRNA expressed in EJ cells.Ad-MK significantly inhibited cell proliferation in a dose- and time-dependent manner.The difference of survival fraction in combined group was statistically significant (P<0.01).Cells treated with Ad-MK plus radiation produced a larger burst size. Conclusion The midkine mRNA is expressed in EJ cells and can selectively replication in them.Ad-MK significantly inhibited cell proliferation in a dose- and time-dependent manner.The cytostatic effects was superior to either virus or radiation treatment alone.Radiation can augment virus replication.