Allograft liver biopsy specimens (n = 24) obtained in the clinical setting of primarily extrahepatic posttransplant lymphoproliferative disease (PTLD) were studied for histopathology, lymphocyte subsets, and Epstein-Barr virus (EBV)-encoded EBER RNA. Acute rejection was found in 20 (83.3%) of 24 biopsy specimens and graded as indeterminate in 7 (35%) of 20 (35%), mild in 3 (15%) of 20, and moderate in 10 (50%) of 20 cases. EBV hepatitis was the primary diagnosis in two biopsy specimens and a secondary finding in six others. Four biopsy specimens showed nonspecific reactive hepatitis, and five showed recurrence of primary liver disease. Immunoperoxidase staining showed primarily T cells. EBER RNA was detected in 14 (58.3%) of 24 biopsy specimens: 12 (60%) of 20 with and 2 (50%) of 4 without acute rejection. Antirejection therapy resulted in complete or partial response in 4 (36.3%) of 11 and 7 (63.7%) of 11 treated cases, respectively, despite the presence of EBV-infected cells in some tissues. Subsequent follow-up showed early or late chronic rejection in 6 (25%) of 24 patients. Gamma glutamyl transferase, a marker for early or late chronic rejection, was greater than five times the upper limit of normal in 9 (37.5%) of 24 patients. In conclusion, liver biopsy specimens in patients with PTLD show a spectrum of pathologic changes. Rejection may be treated even if EBV is concurrently present. Long-term graft is suboptimal, because low immunosuppression results in a tendency to develop chronic rejection.