Persistent nephrotic syndrome that does not respond to treatment may cause progression to kidney failure. We designed a therapeutic protocol with sirolimus for this group of patients. We conducted a prospective, interventional, time series, cohort study lasting 20 months. Thirteen patients were enrolled, with a mean age of 10 years (range: 8-18 years old) with steroid-resistant primary nephrotic syndrome and a histological diagnosis of focal and segmental glomerulosclerosis. We administered sirolimus 3.6mg/m2/day. The duration of this regimen was 12 months in responsive patients. The protocol's efficacy was assessed according to reduction of proteinuria (3 response levels: total, partial, or no response). Severity of histological renal damage and mean time from clinical diagnosis to protocol initiation were also assessed. Nine of 13 patients responded to the treatment with sirolimus, and mean progression time and the severity of histological renal damage influenced response to therapy. We believe that sirolimus is a valid treatment option in patients with steroid-resistant nephrotic syndrome, even though this regimen probably requires an earlier treatment.