OBJECTIVE Preoperative reduction of isoagglutinins leads to successful ABO-incompatible (ABOi) renal transplantation. The strategy includes pretransplantation plasmapheresis, more potent immunosuppressive drugs, splenectomy, and anti-CD20 antibody. It has been reported that low isoagglutinin antibody titers posttransplant were observed among ABOi renal transplants with favorable outcome. The isoagglutinin titers may increase slightly when plasmapheresis is discontinued; however, it never returns to the pretreatment level under immunosuppressive therapy. This raises the question of what occurs to the isoagglutinin titer in ABO-compatible renal transplants under maintenance immunosuppressive pharmacotherapy. METHODS We analyzed 10 renal transplant recipients, including seven living and three cadaveric donors. Patients were treated with basiliximab (20 mg) intravenously on day 0 and day 4. Maintenance immunosuppressive therapy involved a calcineurin inhibitor, mycophenolate mofetil, and steroid. Anti-human globulin isoagglutinin titers were routinely examined 1 day before and day 0 and 1, 2, 3, 4, 8, 12, and 24 weeks posttransplant. No ALG or intravenous immunoglobulin or plasmapheresis treatment was provided in the follow-up period. RESULTS Our preliminary data showed nearly no influence on isoagglutinin titer levels in 6-month follow-up under maintenance immunosuppressive therapy. In addition, no significant difference in isoagglutinin titer was observed between tacrolimus and cyclosporine groups. CONCLUSIONS Maintenance immunosuppressive pharmacotherapy did not affect isoagglutinin titer levels in ABO-compatible kidney transplants. Further study is needed to investigate the mechanisms of persistent low-level isoagglutinin titers among successful ABOi renal transplantation patients.