Inclusion Criteria:

          -  Patients must have histologically confirmed DLBCL with characteristic immunophenotypic
             profiles. Tumor tissue must be confirmed to express the CD20 antigen by flow cytometry
             or immunohistochemistry.

          -  Patients must have at least one site of measurable disease, 1.5 cm in diameter or
             greater.

          -  Patient has not had any previous treatment.

          -  Stage II (not appropriate for abbreviated chemoimmunotherapy and radiotherapy), III or
             IV disease

          -  Able to adhere to the study visit schedule and other protocol requirements.

          -  Patients must have laboratory test results within these ranges:

               -  Absolute neutrophil count > = 1500/mm³

               -  Platelet count > = 75,000/mm³

               -  Serum creatinine < = 1.5X upper limit of normal (ULN)

               -  Total bilirubin < = 1.5X ULN. Higher levels are acceptable if these can be
                  attributed to active hemolysis or ineffective erythropoiesis.

               -  AST (SGOT) and ALT (SGPT) < = 2 x ULN

          -  Disease free of prior malignancies for > = 5 years with exception of currently treated
             basal cell, squamous cell carcinoma of the skin, or carcinoma "in situ" of the cervix
             or breast.

          -  Women of childbearing potential must have a negative serum pregnancy test prior to
             azacitidine treatment.

          -  Women of childbearing potential should be advised to avoid becoming pregnant and men
             should be advised to not father a child while receiving treatment with azacitidine.
             The effects of azacytidine on the developing human fetus at the recommended
             therapeutic dose are unknown. For this reason, women of child-bearing potential and
             men must agree to use adequate contraception (hormonal or barrier method of birth
             control; abstinence) prior to study entry and for the duration of study participation.
             Should a woman become pregnant or suspect she is pregnant while participating in this
             study, she should inform her treating physician immediately.

          -  Age >18 years.

          -  Ability to understand and the willingness to sign a written informed consent document.

          -  ECOG performance status of 0-2

        Exclusion Criteria:

          -  Patients must not have any serious medical condition, laboratory abnormality,or
             psychiatric illness that would prevent the subject from signing the informed consent
             form.

          -  Patients must not have any condition, including the presence of laboratory
             abnormalities, which places the subject at unacceptable risk if he/she were to
             participate in the study or confounds the ability to interpret data from the study.

          -  Use of any other experimental drug or therapy within 28 days of baseline.

          -  Concurrent use of other anti-cancer agents or treatments.

          -  Known positive for HIV or infectious hepatitis B.

          -  Known central nervous system involvement by lymphoma.

          -  Known or suspected hypersensitivity to azacitidine or mannitol.

          -  Patients must not have advanced malignant hepatic tumors.

          -  Pregnant and lactating women are excluded from the study because the risks to an
             unborn fetus or potential risks in nursing infants are unknown.