Acute myeloid leukemia (AML) is a clonal hematopoietic malignancy, characterized by expansion of immature leukemic blasts in the bone marrow. In AML, specific tyrosine kinases have been implicated in leukemogenesis, and are associated with poor treatment outcome. However, targeted therapy using kinase inhibitors (KIs) has had limited success, and may be improved by proper patient selection. We performed phosphotyrosine (pY) based, label-free phosphoproteomics to identify hyperphosphorylated, active kinases in two FLT3+ AML Pt samples.