• Compare the incidence of severe mucositis (CTCAE v3) in HCT patients TAC + MMF to those receiving TAC + MTX for acute graft-versus-host disease (aGVHD).
  

• Incidence of grades II-IV aGVHD and chronic GVHD (cGVHD)- (published clinical staging and grading criteria)
  
• Transplant-related organ toxicity -(CTCAE v3)
  
• Immune reconstitution/T cell turnover - (absolute numbers based on tests)
  
• Engraftment of neutrophils and platelets - (absolute neutrophils count is >500/mm3)& (absolute platelet count is >20,000/mm3)
  
• Length of hospitalization after transplant (date of transplant to the date of discharge)
  
• Days of TPN, narcotic analgesic, and GVHD-related corticosteroid use (record start/stop dates)
  
• Non-relapse mortality at 100 days and 1 year posttransplant
  
• Overall and disease-free survival (time of transplant to the time of relapse/progression or death)
  

The randomization for this comparative trial will be stratified by conditioning regimen and, for those patients enrolled on MCC-14178, by busulfan AUC level.

All patients will receive daily doses of TAC beginning day -3 (day 0 being the day of hematopoietic stem cell transplant (HCT)) and will be given until day +60 when tapering will begin in the absence of GVHD. Provided no GVHD develops, TAC should be discontinued by day +180. Doses will be adjusted to maintain blood levels.

In addition to TAC, patients will be randomized to one of the following additional anti-GVHD medications: MTX or MMF beginning day 0 at least 2 hours after the end of the HCT. In the absence of GVHD a tapering schedule will begin on day +240 and be completed on day +360.

Study participants will be extensively monitored as inpatients and then weekly as outpatients. Some tests will be conducted at least twice weekly (blood tests, toxicity data, GVHD and physical exams) one-month post-transplant and during the tapering off periods for up to 2 years.