Objective To explore the expression of FLT3 on the cells from acute myeloblastic leukemia (AML)and its clinical signficance.Methods The expression of FLT3 from 80 AML cases was measured by FISH.All cases were indentified by karyotyping,40 cases were normal karyotye,and the other 40 cases were abnormal.Results The FLT3 expression level was different in different AML cases.The expression rate in normal karyotype cases was 5.0%,but in abnormal cases 30.7%,in refractory relapse cases 43.3%,in continual complete remission cases 4.5%.The patients’DFS (Disease-Free survival)and OS (overall survival)without FLT3 expression were 65% and 86% in 24 months’following investigation,but the patients’ DFS and OS with FLT3 expression were 20% and 40% respectively.The difference was distinct between them(P<0.05). Conclusion FLT3 can be thought as a new marker for worse prognosis of AML patients,and its expression level is associat-ed with maglignacy-grade.