Inclusion Criteria:

- All patients must have histological confirmation of disease prior to enrollment on
study.

- Patients with de novo AML who are not eligible for induction chemotherapy are
eligible. Patients with refractory, relapsed AML are eligible.

- Patients with AML evolving from prior MDS or secondary to prior chemotherapy are
eligible provided they are not eligible for standard induction chemotherapy.

- Patients with MDS and with blasts > 10% (RAEB-II) are eligible.

- Patients with extramedullary relapse only (i.e., leukemia cutis or other
extramedullary site) are eligible as long as disease can be monitored.

- Patients who have relapsed after standard autologous and/or allogeneic bone marrow
transplant are eligible as long as they meet all other eligibility criteria.

- Patients must not have had any chemotherapy, except hydrea, or radiation for at least
4 weeks prior.

- Patients must be > 18 years of age.

- Patients with an active second malignancy other than non-melanoma skin cancers are
not eligible.

- Patients must have an expected life expectancy of > 12 weeks at the time of
enrollment.

- Patients with visceral, blood stream or nervous system opportunistic infection are
eligible if the infection has been appropriately treated and controlled. Patients
with fungal lung infections must have had treatment for at least one month and have
proof of regression prior to enrollment. Patients may be on antimicrobials at the
time of therapy.

- Initial required laboratory values:

- Total Bilirubin < 2 X upper limit of normal.

- AST & ALT < 3 X upper limit of normal (if elevated liver enzymes thought likely
due to Leukemic infiltrate discuss with the Principal Investigator and the BrUOG
Central Office).

- Creatinine < 2 mg/dl.

- < 15,000 K/uI blast count—Hydroxyurea can be used to decrease count if more
than 15,000 K/ul.

- Patients must have an ECOG performance status of 0-2.

- Patients must receive and sign a full informed consent.

- Patients should not have co-existing medical illnesses which would limit survival <
12 weeks.

- No known history of HIV.

- The safety of decitabine in human pregnancy is unknown. Based on animal studies,
decitabine may cause fetal harm when administered to a pregnant woman. Therefore, it
is important that you do not become pregnant or father a child while receiving study
medication and for 2 months afterwards because the drugs in this study may affect an
unborn baby.

- If you are a woman capable of becoming pregnant (not surgically sterile or
post-menopausal), you must have a negative pregnancy test before beginning treatment.

If you do become pregnant, suspect you are pregnant, or if your partner becomes pregnant
while you are on this study, you must notify your study doctor immediately. If you become
pregnant, you will be taken off this study.

In addition, you must not breast feed at any time you are on this study since any drugs
you are taking may also affect the child.

If you are capable of giving birth to or fathering a child, you must agree to use a form
of birth control (examples of effective birth control are: a condom or a diaphragm with
spermicidal jelly; oral, injectable, or implanted birth control; or abstinence) that is
medically acceptable to your study doctor while taking part in this research study.