Therapy-related acute myeloid leukemias arise as a result of cytotoxic chemotherapy and/or radiation therapy. The most common types of acute myeloid leukemia arising in this setting are acute myeloid leukemia with maturation, and lesser numbers of acute myelomonocytic leukemia, acute monocytic leukemia, acute erythroleukemia, or acute megakaryocytic leukemia. We present a patient with multiple myeloma who was treated with melphalan and 4 years later developed acute erythroid leukemia. The morphologic diagnosis of pure erythroid leukemia developing in the setting of multiple myeloma may be challenging.