FMS-Like Tyrosine kinase 3 (FLT3) plays an important role in early stages of hematopoiesis. FLT3 stimulation enhances proliferation and reduces apoptosis. One potential mechanism of FLT3 involvement in leukemia is over expression of its wild type and its ligand. The FLT3 protein is highly expressed in most patients with AML. In patients with ALL, FLT3 protein is highly expressed in up to 50% of leukemic blasts. Here, we aimed to evaluate the frequency of FLT3 protein expression in pediatric patients with ALL at South Egypt Cancer Institute, Assiut University, Egypt.