Inclusion Criteria:

- Diagnosis of refractory anemia, refractory anemia with ringed sideroblasts and at
least one of the following: a)Anemia with hemoglobin <110g/L and requires at least 1
unit packed red blood cell transfusions every 28 days; b)Thrombocytopenia with
platelet counts <100 x 10^9/L; or c)Neutropenia with absolute neutrophil count <1.5 x
10^9/L.

- OR, Refractory anemia with excess blasts or refractory anemia with excess blast in
transformation, according to the French-American-British classification system for
MDS.

- At least 18 years of age.

- Have a life expectancy of >7 months.

- Unlikely to proceed to bone marrow or stem cell transplantation therapy following
remission.

- Have serum bilirubin levels less than or equal to 1.5 times the upper limit of the
normal (ULN) range for the laboratory.

- Have serum glutamic-oxaloacetic transaminase (aspartate aminotransferase) or serum
glutamic-pyruvic transaminase (alanine aminotransferase) levels less than or equal to
2 x ULN.

- Have serum creatinine levels less than or equal to 1.5 x ULN.

Exclusion Criteria:

- Secondary MDS.

- Prior treatment with azacitidine.

- Any prior history of Acute Myeloid Leukemia (AML).

- Malignant or metastatic disease within the previous 12 months.

- Uncorrected red cell folate deficiency or vitamin B12 deficiency.

- Hepatic tumors.

- Radiation, chemotherapy, or cytotoxic therapy for non-MDS conditions in the previous
12 months.

- Known or suspected hypersensitivity to azacitidine or mannitol.

- Prior transplantation or cytotoxic therapy to treat MDS. Prior use of Revlimid and
Thalomid allowed after 30 day washout.

- Serious medical illness likely to limit survival to less than or equal to 7 months.

- Treatment with androgenic hormones during the previous 14 days

- Active viral infection with known human immunodeficiency virus or vial hepatitis Type
B or C.

- Treatment with other investigational drugs with the previous 30 days.