The FLT3 mutations can be classify into two major types. There are internal tandem duplication (ITD) of the juxtamembrane domain and the other one is a missense point mutation within the activation loop of the tyrosine kinase domain (TKD). Most patients with FLT3-ITD mutation at diagnosis have frequent disease relapse and a short duration of survival when compared to patients without an ITD. Genomic DNA was to detect FLT3 mutations. It was isolated from bone marrow smear slide or peripheral blood of patients at diagnosis using DNA purification kits. The FLT3 mutated regions were amplified by PCR using a genomic DNA template. Considering the ability to predict the prognosis by the presence of FLT3-ITD mutation, this study was designed to screen the mutation in childhood acute leukemia (ALL and AML).