Inclusion Criteria:

- Age greater than or equal to 2 years and less than 18 years of age.

- Diagnosis of a hematologic malignancy.

- Has not received a prior autologous or allogeneic HSCT.

- Is scheduled to receive either a matched family member or MUD bone marrow stem cell
graft at St. Jude Children's Research Hospital. A matched family member donor is
defined as a sibling matched at 5 or 6 HLA loci or another related donor matched at 6
HLA loci.

- Is scheduled to receive a myeloablative preparative regimen (cyclophosphamide/TBI
based) prior to the infusion of the allogeneic graft.

- Cardiac shortening fraction greater than or equal to 25%.

- Serum creatinine is less than twice the upper limit of normal for age.

- Bilirubin less than 3.0 mg/dl.

- Aspartate transaminase (AST) less than 500 IU/ml.

- Alanine transaminase (ALT) less than 500 IU/ml.

- Amylase less than 1.5 times the upper limits of normal for age.

- Lipase less than 1.5 times the upper limits of normal for age.

- Forced vital capacity (FVC) greater than or equal to 40% of predicted value or pulse
oximetry greater than or equal to 92% on room air.

- No known hypersensitivity to E coli-derived proteins or palifermin.

- No active or recent (within 30 days prior to enrollment) gastrointestinal bleeding.

- No active or recent (within 30 days prior to enrollment) oral ulcerations.

- No active fungal infection, bacteremia or viremia within two weeks prior to
enrollment.

Exclusion Criteria:

- Female - pregnant (negative serum or urine pregnancy test within 14 days prior to
enrollment).

- Female - lactating.