This trial is offered to all patients with irreversible intestinal failure who must undergo intestinal, combined liver-intestinal, and multivisceral transplantation at the University of Pittsburgh Medical Center. Patients are recruited through the referral system and no cold calling is carried out. Patient confidentiality is maintained by the use of codes to identify the study participants. All data is stored in a locked filing cabinets as a means to protect participants against a breach of confidentiality. This trial involves ex-vivo low dose irradiation of the intestinal allograft with or without adjunct donor bone marrow cell infusion. An intravenous bone marrow cell infusion is prepared form the thoracolumbar vertebral bodies harvested from cadaveric donors. Control subjects will be those who refuse to be enrolled in the study or those for whom donor bone marrow is not available. All patients will be treated perioperatively with thymoglobulin, a rabbit polyclonal anti-lymphocyte globulin at a dose of 5-10 mg/kg. Tacrolimus will be given in a standard fashion and from the outset as a single monotherapeutic agent to prevent early allograft rejection and promote graft acceptance. All patients will be monitored for rejection, graft function, opportunistic infections and GVHD. Surveillance endoscopy with guided mucosal biopsies will be obtained according to the standard protocol. Attention will be paid for any clinicopathologic changes suggestive of acute or chronic irradiation injuries.