The word aplastic means “unformed”; it is derived from the Greek negative prefix a and plasso, “to form.” In aplastic anemia, blood does not form, leading to deficiencies of granulocytes, platelets, and erythrocytes and to severe clinical consequences, of which infection and bleeding are the most important. In 1935, the course of this disease was considered “progressively, inexorably, and more or less rapidly, fatal” (1). In the past 30 years, morbidity and mortality from aplastic anemia have dramatically decreased because of two effective interventions: allogeneic hematopoietic stem-cell transplantation and immunosuppression with antithymocyte globulin (or antilymphocyte globulin) and cyclosporine. Five-year survival rates are now 70% to 90%. However, clinicians face increasingly complex decisions in selecting the optimal strategy for an individual patient because short-term toxicity, the rapidity and completeness of hematologic recovery, and late complications must be considered.