The study was purposed to investigate the significance of id4 gene promoter methylation in monitoring AML patients with complete remission (CR). Methylation specific-PCR (MS-PCR) were used to detect the status of promoter methylation of id4 gene in bone marrow samples from AML patients with CR who had accepted induction with DA or IA and 4 to 5 consolidation chemotherapy with Ara-C. The results showed that in the all 32 patients, 15 were found to show id4 promoter methylation and 7 out of the 15 were found relapsed or tendency to relapse in the following-up period. While all the 17 patients with id4 unmethylation were still in their CR status in the same period. In conclusion, id4 promoter methylation might be a predictor for relapse of AML patients with CR in certain degree.