Inclusion Criteria:

- Age equal or less than 65 years old and equal to or greater than 18 years old.

- Patients with the diagnosis of MDS or AML with fewer than 5% myeloblasts in the bone
marrow and no leukemic myeloblasts in the peripheral blood on morphologic analysis
performed within 30 days of start of the conditioning regimen enrollment.

- For patients receiving treatment of their MDS or AML prior to transplantation:
a)Interval between the start of the most recent cycle of conventional cytotoxic
chemotherapy and enrollment must be at least 30 days; b)Interval between completing
treatment with a hypomethylating agent or other non-cytotoxic chemotherapy and
enrollment must be at least 10 days.

- Patients must have a related or unrelated bone marrow or peripheral blood donor who
is HLA-matched at 7 or 8 of 8 HLA-A, -B, -C and -DRB1 at high resolution using
DNA-based typing.

- HCT-Specific Comorbidity Index Score (HCT-CI) less than or equal to 4.

- Organ function: a) Cardiac function: Ejection fraction greater than or equal to 40%;
b) Hepatic function: total bilirubin less than or equal to 2 times the upper limit of
normal and ALT and AST less than or equal to 3 times the upper limit of normal.;
c)Pulmonary function: DLCO greater than or equal to 40% and FEV1 greater than or
equal to 50% (corrected for hemoglobin.

- Creatinine clearance greater than or equal to 50mL/min based on the Cockcroft-Gault
formula.

- Signed informed consent.

Exclusion Criteria:

- Prior allograft or prior autograft.

- Symptomatic coronary artery disease.

- Leukemia involvement in the CNS within 4 weeks of enrollment for patients with a
history of prior CNS leukemia involvement (i.e., leukemic blasts previously detected
in the cerebral spinal fluid).

- Karnofsky Performance Score less than 70.

- Patients receiving supplemental oxygen.

- Planned use of DLI therapy.

- Patients with uncontrolled bacterial, viral or fungal infections (undergoing
appropriate treatment and with progression of clinical symptoms).

- Patients seropositive for the human immunodeficiency virus (HIV).

- Patients with prior malignancies, except resected basal cell carcinoma or treated
cervical carcinoma in situ. Cancer treated with curative intent greater than 5 years
previously. Cancer treated with curative intent less than 5 years previously will
not be allowed unless approved by the Protocol Officer or one of the Protocol Chairs.

- Females who are pregnant or breastfeeding.

- Fertile men and women unwilling to use contraceptive techniques during and for 12
months following treatment.