Survival of patients with severe acquired aplastic anemia has improved dramatically during the past decade mainly due to the use of new treatments. The long-term follow-up of these patients has allowed to observe an increased incidence of late malignant hematological complications such as myelodysplastic syndromes and leukemia, which raises the question whether they are just different forms of presentation of the same disease. We report two cases of severe acquired aplastic anemia with long-time survival, one of them developed a myelodysplastic syndrome and the other one a myelodysplastic syndrome followed by an acute leukemia. We discuss the factors associated with a high risk to develop myelodysplastic syndrome and acute leukemia, and its repercussions in therapy.