Myelodysplastic syndrome (MDS) is relatively common in the elderly, and aging of populations is progressing in developed nations, notably so in Japan. The major age group in Japan and Sado Island are distributed between 30 and 60 and between 50 and 80, respectively. The aim of this study was to analyze the features of MDS in the population of Sado Island to anticipate the characteristics of the disease in the near future. One-hundred and fifty-three patients (71 male, 82 female, 19-94 years old, median 73 years old) with de novo MDS between 1985 and 2005 were retrospectively evaluated. All patients were reclassified according to WHO-2001 criteria. The predictive power of the international prognostic scoring system and the WHO classification-based prognostic scoring system were evaluated. The major causes of death were leukemic transformation (38%) in refractory anemia with an excess of blasts and infection (48%) for total MDS. Age was another independent prognostic factor. Elderly patients exhibited a significantly poorer prognosis mainly due to infections such as pneumonia. Although novel remedies for MDS and hyperferremia have recently been developed, prevention of infection remains important in MDS, particularly for older patients.