Thrombocytopenia is common among liver transplant candidates and recipients. The aim of our study was to determine the incidence and outcome of new-onset immune-mediated thrombocytopenic purpura (ITP) following liver transplantation at a single center. Among the 256 liver transplant recipients with an International Classification of Diseases, Ninth Edition code for thrombocytopenia, 8 cases of new-onset ITP were identified, leading to an overall incidence of 0.7% in 1,105 consecutive liver transplant recipients over a 15-year period. All 8 patients were Caucasian, 5 (63%) were male, and the median age at ITP onset was 54 years (range, 15-63). The median platelet count at presentation was 3,500 cells/mL (range, 1,000-12,000) and liver disease was due to hepatitis C (38%), primary sclerosing cholangitis (38%), and cryptogenic cirrhosis (25%). The median time from transplant to ITP onset was 53.5 months (range, 1.9-173). Three of the 6 patients tested (50%) had cell-bound antiplatelet antibodies, 1 patient had an underlying hematological malignancy, and none of the organ donors had a history of ITP. Corticosteroids and/or immunoglobulin infusions were effective in 4 patients. However, serial rituximab infusions were required in 4 patients with persistent thrombocytopenia, and 3 of them eventually required splenectomy to induce disease remission. At a median follow-up of 19.7 months, 7 long-term survivors remain in remission with a median platelet count of 267,000 cells/mL. In conclusion, new-onset ITP is an infrequent but important cause of severe thrombocytopenia in liver transplant recipients. Corticosteroids and immunoglobulin infusions were effective in 50% while the remainder of patients required rituximab infusions or eventual splenectomy for long-term disease remission. Liver Transpl 12:781–791, 2006. © 2006 AASLD.