OBJECTIVE To investigate the methylation status of the promoter of resion death associated protein kinase (DAPK) gene in bladder cancer cell (T24), and study the effect of 5-aza-2'-deoxycytidine (5-aza-dc) on DAPK gene reactive expression in T24 and its inhibitory effect on T24. METHODS The bladder cancer cell T24 was treated with different doses of 5-aza-dc. The inhibitory effect and apoptosis rate were detected by MTT and flow cytometry, and the changes of DAPK mRNA and protein expression and the methylation status of DAPK promoter were assessed by RT-PCR, Western blotting, and methylation specific PCR, respectively. RESULTS The growth of bladder cancer cell was inhibited significantly and the maximal apoptosis rate detected by flow cytometry was (24.12-/+1.4)%. DAPK mRNA was not expressed in bladder cancer cell T24 in normal conditions. DAPK mRNA and protein re-expressed after 5-aza-dc (12.5 micromol/L) treatment in cell line T24 for 24 h, and DAPK promoter became unmethylated. CONCLUSIONS The promoter methylation can be an important factor for silencing the expression of DAPK in bladder cancer cell. 5-aza-dc can inhibit the growth and induce apoptosis of bladder cancer cells through reversing unmethylation status of DAPK promoter.