A 69-year-old male patient with refractory anemia with excess blasts (RAEB) was found to have a consistent chromosomal abnormality, t(6;9)(p22.3;q34), in the bone marrow and unstimulated peripheral blood cells. Twenty patients with t(6;9) and leukemia have been reported; some of them had a myelodysplastic syndrome (MDS) before developing overt ANLL. Our patient was still in the MDS stage when the t(6;9) was found. This result suggests that t(6;9) represents one of the pathways from MDS to leukemia in patients with ANLL.