Objective:To investigate the relationship between resistance to TRAIL and methylation status of DR4 and DR5 in bladder cancer cell lines. Methods:T24 and BIU87 bladder cancer cell lines were employed in the study of mRNA expression DR4 and DR5 inbladder cancer cells were detected using reverse transcription polymerase chain reaction(RT-PCR). DNA methylation status of wes examined by methylation specific polymerase chain reaction(MSP) in bladder cancer cells with low expression of DR4 and DR5 mRNA. Furthermore,bladder cancer cells were exposed to TRAIL and TRAIL combined 5-aza-2,-deoxycytidine(AzadC) to measure cancer cells growth and apoptosis by Flow Cytometry. Results:No DR4 and DR5 expression were detected in T24 cell line by RT-PCR. The methylation status was determined and correlated with the expression pattern. We observed DR4 and DR5 promoter hypermethylation. In contrast,DR4 and DR5 hypermethylation could not be found in BIU87 cell line which remained DR4 and DR5 expression. The apoptosis rates of T24, BIU87 bladder cancer cells treated with 100 ng/ml TRAIL singly were 7.6%, 30.4% respectively,which had significant difference compared with the groups without treatment(P < 0.05). However the apoptosis rates of T24 and BIU87 cell lines treated by 100 ng/ml TRAIL combined with 5 μmol/L AzadC reached 29.2%,31.7% respectively. Conclusion:Our findings showed a functional relevance of the DR4,DR5 expression in T24 cell line and suggested a substantial contribution of DR4,DR5 hypermethylation and consequent loss of DR4,DR5 expression in bladder cancer.