BACKGROUND For years ABO-incompatible kidney transplantations were preferentially performed in Japanese centers. In order to overcome the increased risk of humoral rejections, patients were treated with multiple sessions of plasmapheresis, intensified immunosuppressive therapy and splenectomy before transplantation. Despite good long-term results regarding patient and organ survival rates, increased morbidity during the early post-transplant period prevented a broad application of this method. Recently, a new protocol including the anti-CD20-antibody (Ab) rituximab and blood group-specific immunoadsorption instead of splenectomy and plasmapheresis was published with excellent short-term results. METHODS From April 2004 to September 2005, 11 patients were prepared for ABO-incompatible transplantation. All patients received 375 mg/m2 rituximab intravenous 3 to 4 weeks before transplantation. Immunosuppressive therapy consisted of tacrolimus, mycophenolate mofetil and prednisone and was started at least 7 days before transplantation. Intravenous immunoglobulins (0.5 g/kg) were administered the day before transplantation. Immunoglobulin G (IgG)-anti-A or -B Ab titers before starting immunoadsorption treatment ranged between 1 : 4 and 1 : 1024. Immunoadsorption treatment was started in parallel with immunosuppressive medication and was continued until the anti-A or anti -B Ab titers (IgG and IgM) were lowered to the aimed pre-transplant threshold of <1 : 8. During the early postoperative period, additional immunoadsorption treatments were performed, if the titers increased again above 1 : 8 (days 0 to 7) or 1 : 16 (days 8 to 14), respectively. RESULTS Transplantation could be conducted in eight of 11 patients (two females, six males, mean recipient age 52+/-11 yr). The mean follow-up was 7.0 months (range 4 to 17). The blood group constellation was A1 to 0 in four cases, A2 to 0 in two cases, B to A in one case, and A1 to B in another case, respectively. On average, each patient received seven immunoadsorption treatments. All transplants showed primary function and no humoral rejections occurred. Three of our 11 patients showed rapid increases of isoagglutinin titers after each immunoadsorption treatment and thus could not be transplanted. One patient died 4 months after transplantation with a functioning graft due to sepsis secondary to pseudomembranous enterocolitis. The mean creatinine value of the remaining seven patients now is 1.6 mg/dl. CONCLUSIONS The use of antigen-specific immunoadsorption and an immunosuppressive regimen consisting of a conventional triple immunosuppressive therapy has shown excellent short-term results. The immunoadsorption treatment using antigen-specific columns is highly effective and even patients with high isoagglutinin titers can be transplanted. This protocol is an option for end-stage renal disease patients who have no blood group-compatible donor.