Focal segmental glomerulosclerosis (FSGS) is known to recur in some patients after renal transplantation. Over a prolonged period, we followed 13 pediatric patients with FSGS who had undergone transplantation from living-related donors, analyzing risk factors for recurrent disease. Native nephrectomies were performed bilaterally in all patients at least 1 month prior to transplantation. Immunosuppressive therapy consisted of cyclosporine (CyA), mizoribine, prednisone, and antilymphocytic globulin or deoxyspergualin. We examined age at onset, time in months between diagnosis and end-stage disease (dialysis or transplantation), the duration of dialysis, age at transplantation, time since nephrectomy, doses of immunosuppressive agents, and HLA mismatch. Five patients (42.8%) developed recurrent disease in the graft; all showed proteinuria within 24 h of transplantation. However, all allografts have functioned well for 34-156 months following transplantation despite the recurrences, although 1 of these patients now shows proteinuria. The remaining 8 patients have had no recurrence for 104.6+/-30.4 months (mean+/-SD). The serum level of creatinine in patients with recurrence and without recurrence was 1.1+/-0.42 mg/dl and 0.98+/-0.29 mg/dl, respectively. The interval from diagnosis to initiation of dialysis was significantly shorter in patients with recurrence than those without recurrence ( P<0.05), but no other variables differed between these two groups. No recurrence of FSGS was observed in the protocol biopsy at 100 days after transplantation. We believe that CyA and native nephrectomy may limit or reverse progression of recurrent FSGS in renal allografts of Japanese pediatric patients, although this is a limited study.