We report here a case of donor cell leukemia in a female Ph-positive CML patient who received an allogeneic BMT from her HLA-identical brother in the chronic phase and subsequently developed a donor cell Ph-positive ALL. The number of cases of donor cell leukemia after BMT so far reported is less than 20 and in this case, as in the first cases reported by Marmont et aland McCane et al, the original leukemia and donor cell leukemia share the presence of a Ph chromosome. Furthermore, we analyzed the patient during different stages of her disease by RT-PCR and determined the type of bcr-abl junctions (M bcr-abl junction; b3a2 transcript, p210) in both the recipient and donor cell leukemia.