The myelodysplastic syndromes are clonal hematopoietic stem cell disorders characterized by varying degrees of pancytopenia and often a progression to acute myeloid leukemia. Recent evidence has linked myelodysplastic syndromes to environmental and occupational genotoxic exposure. Specific cytogenetic abnormalities are well described in myelodysplastic syndromes and have been demonstrated to be useful diagnostic and prognostic tools. Activation of protooncogenes such as ras and fms have also been noted in myelodysplastic syndromes; however, their contribution to the pathogenesis of the syndrome remains to be determined. Aggressive leukemia-like induction therapy, differentiating agents (low-dose cytarabine, 13-cis-retinoic acid) have had little impact on overall survival in myelodysplastic syndromes. The recombinant hematopoietic growth factors (granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor) may be of significant benefit to patients with myelodysplastic syndromes, although it remains to be determined whether they will have a substantial impact on survival. Allogeneic bone marrow transplantation is the only potentially curable treatment of myelodysplastic syndromes. The advanced age of these patients as well as the lack of histocompatible donors restricts this modality to only a small proportion of patients.