We report a case of a 2-year-old boy with steroid- and ciclosporin (CsA)-resistant collapsing focal segmental glomerulosclerosis (FSGS) who went into complete remission with a combination of IV rituximab and methylprednisolone pulse therapy (MPT) while receiving oral CsA. He was initially treated with steroids including MPT, CsA, and plasmapheresis, but his massive proteinuria and severe systemic edema persisted. We treated him with four weekly doses of intravenous rituximab. After the second administration of rituximab, his proteinuria and systemic edema were dramatically improved, but hypoalbuminemia and proteinuria persisted. Eight months after the onset, he was re-treated with two courses of MPT. Thereafter, he finally went into complete remission 1 month after MPT. He continued in remission for 8 months with CsA, but then relapsed. However, he went into complete remission again with 60 mg/m(2) of oral prednisolone without rituximab and since then, he has been in remission with CsA. This is the first report of the successful treatment of collapsing FSGS with rituximab. Thus, rituximab emerges as a new therapeutic option against refractory collapsing FSGS.