Clonal cytogenetic abnormalities are found in about 50% of all patients with myelodysplastic syndrome (MDS) and the clinical implication of these abnormalities is now well documented. However, the de novo appearance of balanced translocations in MDS patients during the progression of the disease is rarely reported and the significance of the balanced translocation remain to be elucidated. We report here the first case of refractory anemia with excess blasts in transformation (RAEBt), in which a new chromosomal translocation, t(7;13)(q10;q33) appeared de novo in the AML phase. It has been revealed that rearrangements and deletions of chromosome 7, i.e. der(1;7)(q10;p10), are very complex and that multiple regions may contribute to the disease phenotype and progression. Our case suggests that the chromosomal region at 7q10, rather than 1p10, might be one of the hot spots for myeloid proliferative disorders, including MDS.