De novo autoimmune hepatitis has been described in both pediatric and adult liver transplantation (LT) recipients. Studies of small numbers of patients have proposed it to be an alloimmune hepatitis or form of chronic rejection. We have recently noted an increasing number of patients with post-LT recurrent hepatitis C virus (HCV) developing this, with an apparent negative impact on outcome and survival. We term this entity posttransplant plasma cell hepatitis (PCH). A search of our institution's pathology database was performed with the terms “plasma cell(s),” “lymphoplasmacytic infiltrate,” and “liver allograft.” A histological scoring system was devised to more reliably diagnose PCH in the setting of recurrent HCV. Thirty-eight patients were identified, and their clinical data were analyzed. Sixty percent had a negative outcome as defined by the development of cirrhosis, need for retransplantation, or death. Eighty-two percent had recent lowering of immunosuppression or subtherapeutic calcineurin inhibitor levels; 58% developed PCH within 2 years post-LT. Histologic resolution of PCH was associated with good outcome (P < 0.001). Patients not receiving treatment had a negative outcome (P = 0.007) as did patients receiving corticosteroids as therapy (P = 0.02). Persistence (P = 0.007) or recurrence of PCH was associated with negative outcome. In conclusion, PCH is a histologic variant of rejection. On liver biopsy, PCH can at times be difficult to diagnose, and the use of a standardized scoring system is recommended to differentiate it from other forms of allograft dysfunction. Treatment by optimization of immunosuppression without the use of corticosteroids appears effective. The development of PCH in the setting of recurrent HCV is a negative prognostic factor for patient outcome and allograft failure. Liver Transpl 14:861–871, 2008. © 2008 AASLD.