A predominance of total or partial chromosomal losses and the rarity of translocations are characteristics of myelodysplastic syndrome (MDS), and 5q,-5, -7 and +8 are known to be the most predominant chromosomal changes. To investigate whether the incidence and the pattern of chromosomal changes in MDS varies by location in Korea, we reviewed the cytogenetic results of 205 MDS cases from three medical centers. Distribution of MDS subtypes and the incidence of chromosomal aberration (44.8%) of MDS in Korea were similar to those found in other countries, however, their patterns were different. Translocations (40.4%) predominated over partial or total deletions (36.3%) in Korea. The most common abnormalities in MDS were trisomy 8, trisomy 1q, -5/5q-, and -7/7q-, which occurred in 18(19.5%), 14(15.2%), 12(13.0%), and 11(11.9%) patients, respectively. It is of note that trisomy 1q, which is rarely reported in hematologic malignancies, was the second most common change associated with MDS in Korea, and that structural anomalies of chromosomes 1(19.6%) exceeded that of chromosome 5(15.2%). The most common sole anomalies were trisomy 8(7.6%) and 14(78%) of 18 cases with chromosome 1 anomalies accompanied by other chromosomal abnormalities, suggesting that the changes of chromosome 1 may be evolutionary events rather than sporadic events. In conclusion, trisomy 1q and trisomy 8 predominate in Korean MDS, suggesting the likelihood of ethnic differences.