Myelodysplastic syndromes (MDS) are clonal hematological disorders characterized by ineffective hematopoiesis. Their increased prevalence is associated with the aging of the population. The aim of this article is to analyze the available literature about MDS - its classification, pathophysiology, prognosis and recent progress in treatment - and report our experience with it. Its diagnosis and classification are based on the morphological features of blood and bone marrow cells. The World Health Organization (WHO) working group has proposed a new classification to improve the homogeneity of the categories in the widely-used French-American-British classification in term of pathophysiology and prognosis. This new classification permits the consideration of clinical, etiologic, and cytogenetic data, including complex and heterogeneous cytogenetic abnormalities. The International Scoring System for evaluating Prognosis (IPSS), which has proven highly useful for this purpose, is a risk-based classification system for MDS, based on these cytogenetic abnormalities. It can be used to help guide therapeutic choices. For MDS with low IPSS scores (low-risk), appropriate treatment includes best supportive care, hematopoietic growth factors, and immunomodulatory drugs. For MDS with high IPSS scores, chemotherapy is appropriate at low or intense doses. For younger patients, allogeneic bone marrow transplantation, the only truly curative treatment, may be considered. Better understanding of the pathophysiology of MDS, including the role of oncogenes and various cytokines, is required to develop new treatments and treatment targets. The new classification and prognosis scoring system should lead to new therapeutic strategies that may modify the overall prognosis and quality of life of patients with MDS.