Inclusion Criteria:

- The patients diagnosed with (primary or secondary) Myelodysplastic Syndrome including
chronic myelomonocytic leukemia (CMML)

- Patients with an International Prognostic Scoring System >= Int-1

- Patients who have never treated with hypomethylating agent(azacitidine and
decitabine)

- Female patients who are postmenopausal or received contraceptive operation or refrain
from sexual relations. Women of childbearing potential should conduct an effective
method of birth control (oral contraceptives, injections, intrauterine device, double
barrier method, contraceptive patch and male partner's sterilization),in case of male
patients who will not have a baby within 2 months after the completion of decitabine
therapy

- Patients who signed an informed consent document indicating that they understand the
purpose of and procedures required for the study and are willing to participate in
the study

Exclusion Criteria:

- Patients diagnosed with acute myelogenous leukemia (AML, bone marrow stem cell counts
exceeding 20 %) or other progressive malignant diseases

- Patients with active infection of virus or bacteria

- Patients who used to be treated with azacitidine or decitabine

- Patients who are hypersensitive to excipients of decitabine

- Patients who are pregnant of breast-feeding