In order to determine whether the clinical differences among the various AML oncogenes are reflected during the in vitro transformation of primary human cells, retroviral vectors expressing AML1-ETO, PML-RARA, MLL-AF9, or NUP98-HOXA9 were used to transduce human CD34+ hematopoietic progenitor/stem cells from mobilized peripheral blood. The gene discussed is HOXA9; the disease is acute myeloid leukemia.