The myelodysplastic syndromes are a group of hematologic disorders that adversely affect the levels of hemoglobin, platelets, erythrocytes, and leukocytes. Although the cause of this syndrome is unknown, new diagnostic techniques have facilitated identification and classification of these diseases into five categories: refractory anemia (refractory cytopenia), refractory anemia with ringed sideroblasts, refractory anemia with excess blasts, refractory anemia with excess blasts in transformation, and chronic myelomonocytic leukemia. Cytogenetic abnormalities may be present in more than 55% of the patients. Symptomatic patients should be assessed relative to life-threatening versus non-life-threatening cytopenias and age. Management consists of primarily supportive measures, although certain approaches that are currently being used or under investigation, such as concomitant administration of erythropoietin and other growth factors, show promise for the future.