The fusion gene AML1/ETO is a molecular marker for monitoring minimal residual disease (MRD) in acute myeloid leukemia with the t(8;21)(q22;q22) translocation. To evaluate the dynamic variation and prognostic significance of AML1/ETO, bone marrow samples from 52 patients at different periods were examined qualitatively (32 patients) or quantitatively (20 patients) using nested RT-PCR and RQ-PCR, respectively. In the qualitative group, AML1/ETO in 71.88 and 95.45 % patients became negative at six and 24 months after CR, respectively. Patients in long-term remission were all RT-PCR-negative. Patients negative for AML1/ETO at 6-12 months and 12-18 months after CR had lower relapse rate (P = 0.003 and 0.000), higher relapse-free survival (RFS) (P = 0.000 and 0.000), and overall survival (P = 0.001 and 0.000) than patients with positive AML1/ETO. Quantitative analysis showed that there was no trend where higher relapse rate occurred in patients with higher levels of AML1/ETO transcripts at diagnosis (P > 0.05). Patients whose AML1/ETO transcripts decreased by more than 2 log at CR had higher RFS (P = 0.02). At the checkpoints of 3 and 5/6 months after CR, patients with lower AML1/ETO copy numbers showed lower probability of relapse (P = 0.039 and 0.004). An increase of AML1/ETO transcripts (0.5 log) at any time after CR indicated increased risk of relapse (P = 0.002). Our study shows that both qualitative and quantitative detection of AML1/ETO have prognostic value in MRD monitoring. Negative or continuous low expression of AML1/ETO indicates increased disease-free survival.