OBJECTIVE Fms-like tyrosine kinase 3 internal tandem duplication (FLT3/ITD) is associated with an unfavorable prognosis in acute myeloid leukemia (AML). However, the role of FLT3 expression as well as its correlation to FLT3/ITD has not sufficiently studied. This study was to evaluate the relationship between FLT3 gene expression and FLT3/ITD mutation in patients with de novo AML. METHODS FLT3 gene expression was determined by real-time quantitative polymerase chain reaction (RQ-PCR). FLT3/ITD mutation was detected by PCR in 79 de novo AML patients. RESULTS FLT3/ITD mutations were found in 22.8% (18/79) patients. FLT3 gene expression (range: 0-7320, median: 312) was detected in 92.4% (73/79) patients, but not in normal controls. Compared to AML patients with low FLT3 expressers and without FLT3/ITD mutation, patients with high FLT3 expressers and FLT3/ITD mutation had a significantly higher white blood count as well as a higher ratio of bone marrow blasts. The positive rate of FLT3/ITD mutation was not correlated to the level of FLT3 expression, and no statistical difference of FLT3 expression was found between AML patients with and without FLT3/ITD mutation. The complete remission (CR) rate of AML patients with FLT3/ITD mutation (58.8%) was significance lower than that of those without FLT3/ITD mutation (82.1%). In AML patients without FLT3/ITD mutation, the CR rate was significantly lower in patients with high FLT3 expressers (69.2%) than in those with low FLT3 expressers (93.3%). CONCLUSIONS The FLT3 expression is not associated with FLT3/ITD mutation. High-FLT3 expression may be a poor prognostic factor for AML patients without FLT3/ITD mutation.