Secondary myelodysplastic syndrome/acute myelogenous leukemia (MDS/AML) are today considered a primary complication of autologous hematopoietic stem cell transplantation. In our Center, 83 autografted patients underwent bone marrow (BM) biopsy and cytogenetic analysis at fixed intervals. Twelve patients developed non-clonal cytogenetic abnormalities and 10 patients clonal abnormalities, five of whom (three - 7, one - 5 and one t(9;11)) developed secondary MDS/AML. MDS was also diagnosed in two patients with a normal karyotype. In brief, seven patients (three males, four females; median age 36 years) developed MDS/AML 12-48 months (median 14) after autografting. The FAB diagnosis was AML-M2 in one, chronic myelomonocytic leukemia in two and refractory anemia with excess of blasts in transformation in four cases. Two patients presented a BM biopsy picture of MDS with fibrosis; none of them experienced leukemic transformation. Four MDS patients died, three of leukemic transformation and one of BM insufficiency; the two remaining patients are still living and untransformed. Our data underline the leukemogenic role of previous treatments, even if it is not possible to exclude that underlying disease and/or conditioning therapy may be involved.