Inclusion Criteria:

- Disease Status

- AML 1st CR with a matched family donor (excluding Downs Syndrome, APL, and
patients consented to and registered on an upfront AML COG study with a matched
family donor)

- AML 1st CR [excluding Downs Syndrome, APL, and chromosome translocation (8;21)
or inversion (16)] with unrelated donor

- AML 2nd CR

- MDS and < 5% bone marrow myeloblasts at diagnosis (de novo patients only)

- JMML and < 5% bone marrow myeloblasts at diagnosis

- Disease must express a minimum of >10% CD33 positivity for patients with AML

- Patients must have adequate organ function as defined below:

- Adequate renal function defined as:

- Serum creatinine < 1.5 x normal, or

- Creatinine clearance or radioisotope GFR 40 ml/min/m2 or > 60 ml/min/1.73 m2
or an equivalent GFR as determined by the institutional normal range

- Adequate liver function defined as:

- Total bilirubin 2.0 x ULN, or SGOT (AST) or SGPT (ALT) < 5.0 xULN

- Adequate cardiac function defined as:

- Shortening fraction of > 25% by echocardiogram, or

- Ejection fraction of > 45% by radionuclide angiogram or echocardiogram

- Adequate pulmonary function defined as:

- DLCO > 40% by PFT (Uncorrected)

- For children who are uncooperative, no evidence of dyspnea at rest, no exercise
intolerance, and a pulse oximetry > 94% on room air

Exclusion Criteria:

- Patients with active CNS AML/JMML disease at time of preparative regimen

- Secondary MDS

- Female patients who are pregnant (positive HCG)

- Karnofsky <70% or Lansky <50% if 10 years or less

- Age >65 years

- Seropositive for HIV

- Patients consented to and registered on an upfront COG AML study with a matched
family donor