Background.Early recurrence of massive proteinuria after renal transplantation occurs in 20% to 30% of patients with steroid-resistant idiopathic nephrotic syndrome and is responsible for graft failure in approximately half of cases. We report our experience with the use of intravenous (IV) cyclosporine (CsA) in children with recurrent proteinuria after renal transplantation.Methods.Between March 1991 and August 2001, 36 renal transplantations were performed in 35 patients with steroid-resistant idiopathic nephrotic syndrome in our institution. Recurrence, defined by proteinuria higher than 50 mg/kg per day in the absence of acute rejection or urinary tract infection, was observed in 17 grafts performed in 16 patients. In patients with recurrence, CsA was administered IV, at an initial dose of 3 mg/kg per day, which was afterward adapted to maintain whole-blood levels between 250 and 350 ng/mL.Results.In 14 of 17 cases (82%) with recurrence, proteinuria completely disappeared after 20.8±8.4 (range 12–40) days. The treatment was ineffective in the remaining three patients with persistent proteinuria at the end of the second month posttransplantation. Plasma exchanges were performed in four patients during the first 2 months, and proteinuria regressed in three cases and persisted in one. Persistent remission was observed in 11 patients with a follow-up of 3.7±3 (range 0.3–9) years. Actuarial graft survival was 92% and 70% at 1 and 5 years.Conclusion.IV CsA is a safe and effective treatment in children with recurrent nephrotic syndrome after renal transplantation.