Two human homeobox genes, HB9 and HLX, are expressed in hematopoietic progenitors and activated lymphocytes. They are implicated in the proliferation of hematopoietic progenitors in response to growth factors and the differentiation of hematopoietic progenitors to mature cell lineages. RNAs from bone marrow cells of patients with acute myeloid or lymphocytic leukemia have high levels of these two genes while similar RNAs from patients with chronic lymphocytic or myeloid leukemias have nearly normal levels. While the significance of these two genes in leukemogenesis is unknown, they are likely to regulate gene transcription during hematopoiesis and their dysregulation may have dire consequences for hematopoietic cells.