The invention features methods for characterizing and treating acute myeloid leukemia (AML) (e.g., newly diagnosed, relapsed, and refractory AML) in a subject using immunoconjugates of the invention. In one aspect, the invention generally features a method of treating acute myeloid leukemia in a subject (e.g., a human), the method involving administering an effective amount of an immunoconjugate to a pre-selected subject, where the immunoconjugate contains a humanized or chimeric antibody or fragment conjugated to a cytotoxic benzodiazepine dimer compound via a cleavable disulfide linker.