Myelodysplastic syndrome (MDS) is a morphologically characterized hematologic entity that is one of the clonal myeloproliferative disorders. Approximately 50 approximately 70% of MDS patients have cytogenetic abnormalities; these are usually chromosomal deletions, but some involve translocations such as t(1;7) (q10;p10). Translocations involving chromosomal regions 3q26 or 22q11 are often therapy-related. Recent studies have demonstrated that cytogenetic changes in MDS patients have clinical relevance. Accordingly, there are now scoring systems for predicting the prognoses of MDS patients. In this review, we describe the clinical significance of cytogenetic changes in MDS. We include MDS with some atypical forms, such as MDS with hypocellular bone marrow, MDS with minimal dysplasia, and MDS with myelofibrosis.