Posttransplant lymphoproliferative disorders (PTLD) are abnormal growths of lymphoid cells that occur in immunosuppressed organ transplant recipients. Most cases are of B-lymphocyte origin and are associated with Epstein-Barr virus infection. Twelve of 72 allograft recipients with PTLD in our series have had disease predominantly involving the gastrointestinal tract. The lesions are most often multiple and preferentially involve the distal small bowel. The appearance of the lymphoid cells ranges from nonuniform (polymorphic) to uniform (monomorphic). Most tumors contain a clonal component of B-lymphocytes, with or without a nonclonal background. Appropriate primary treatment includes surgical resection and reduction of immunosuppression. Occasional PTLD of the gastrointestinal tract do not respond to this regimen, these represent a more advanced state of tumor progression. Currently, 11 of 12 patients are alive 10-13 months after diagnosis. The surgical pathologist must be aware of the appropriate setting in which to consider a diagnosis of PTLD and be able to distinguish this condition from other lymphoproliferative disorders of the gastrointestinal tract.