The expression of octamer binding factor 4 (Oct4) gene in bladder cancer cell line T24 and its effects on the biological characteristics of the cells were investigated.RT-PCR and West blot were employed to detect the expression of Oct4 in T24 cells.The changes of biological charac-teristics in T24 cells were analyzed before and after gene-silencing by Boyden chamber and MTT.The results showed that the expression of Oct4 gene was detectable in T24 cells by RT-PCR and West blot.The expression of Oct4 gene and protein was down-regulated by siRNA,and average number of transwell cells in interference group,negative control group and blank control group was 101.40±4.56,104.20±10.03 and 111.00±11.90,respectively.There was significant difference in the proliferation ability of the cells from 48 h,72 h to 96 h after the interference by siRNA between in-terference group and negative group or blank control group (P<0.05).It was suggested that Oct4 gene was related with proliferation ability ofT24 cells,but not with invasive capability.