P520 Aims: The donor shortage problem encouraged us to perform living donor liver transplantation (LDLT) across the ABO blood barrier. The survival rate in ABO-incompatible transplantations was much poorer than in ABO-compatible recipients for the early experiences, but the introduction of novel immunosuppressive regimens and PE has yielded excellent results in ABO-incompatible transplantations. We have successfully performed 3 cases of ABO-incompatible LDLT by using rituximab. Methods: In our institution we experienced 10 ABO-incompatible recipients out of 79 LDLT and 3 out of 10 recipients were administered rituximab for rescue or prophylactic therapy. The age range of the 10 recipients was 7 months to 54 years, with median age of 12.8 years. IgM and IgG hemagglutinin titers were measured before and after Tx using serial dilution in saline. Pre-Tx PE was performed as necessary to maintain hemaggulutinin titers below 1:16 and post-Tx PE was performed when it was diagnosed as hyperacute rejection with high titers. Induction immunosuppression consisted of FK506, steroid and MMF. Results: Nine of the 10 recipients and all the 3 recipients who were administered rituximab were alive. Case1 : A 22 months old girl whose primary disease was BA was performed LDLT from her father (A to O). She was also performed PE for twice before Tx in order to reduce titers 16 or below. From POD 3 the titers and LFTs were elevated despite the PE. On POD 7 needle graft biopsy revealed the hyperacute rejection and she was treated by rituximab, DSG and steroid pulse therapy. Her titers and LFTs were improved drastically and she was discharged on POD 74. CD19 positive lymphocytes in her peripheral blood were less than 1% until 3 month after Tx. Currently, 22 months after Tx, she is in stable condition. Case2 : A 42 year old woman whose primary disease was PBC was performed LDLT from her brother in law (B to O). She was performed PE for 7 times before Tx because of the high titer (1:512) and was administered rituximab prophylactic just after Tx. She also had splenectomy and intrahepatic artery infusion of PGE1 and steroid for 2 weeks. One week after Tx the titers were elevated with slight deterioration of LFTs, steroid pulse with PE improved the LFTs. She was discharged on POD 102 due to biliary leakage. CD19 positive lymphocytes in her peripheral blood were less than 1% until 8 month after Tx. Currently, 12 months after Tx, she is in stable condition. Case3 : A 54 year old woman whose primary disease was LC(B) with HCC was performed LDLT from her son (A to O). She was performed PE for 3 times before Tx and was administered rituximab prophylactic just after Tx. Because her hepatic artery was dissected during the Tx, she had intraportal infusion of PGE1 and steroid for 2 weeks and she also had splenectomy. Until 1 month after Tx her LFTs was stable and no sings of rejection was occurred. CD19 positive lymphocytes in her peripheral blood were 6 % after 1 month. Conclusions: Rituximab has the possibility to become the new strategy for the ABO-incompatible liver transplantation.