Use of Sirolimus in five pediatric patients undergoing solid organ transplantation Background: Sirolimus (SRL) is an immunosuppressive drug increasingly used in children undergoing solid organ transplantation. SRL does not cause glucose intolerance, hypertension, nephrotoxicity or neurotoxicity, offering significant potential advantages over calceneurin inhibitors (CNI). Aim: To report five children treated with SRL. Material and methods: A retrospective review of four children undergoing orthotopic liver transplantation (OLT) and one undergoing renal transplantation with recurrent acute rejection (RAR), chronic rejection (CR) or toxicity due to CNI, treated with SRL between June 2001 and November 2006. Results: As primary immunosuppressive therapy, all patients received 3 drugs: CNI (Tacrolimus (FK) or Cyclosporine), mycophenolate mofetil and steroids. Mean age at treatment with SRL was 98 months. Children undergoing OLT had a late introduction of SRL (mean time after OLT: 37 months), and mean follow-up was 24 months. In this group rescue indications of SRL were RAR in one, CR in one, thrombotic thrombocytopenic purpura (TTP) in one, food allergy in one and other CNI toxicity in three. Only one did not experience adverse events due to SRL, but no one required discontinuation of SRL. There were remissions of RAR, CR, TTP and food allergy. The patient with RT was switched from FK to SRL at day 18 th after RT, but he had severe neutropenia that led to discontinuation of SRL. Conclusions: SRL may be useful in pediatric solid organ transplant recipients suffering from RAR, CR, TTP, food allergy and CNI toxicity. Careful attention should be directed to detect side effects and avoid severe complications (