BACKGROUND Patients with severe or progressive idiopathic membranous nephropathy (IMN) should receive immunosuppressive therapy (IST). Alkylating agents, corticosteroids and cyclosporine A (CsA) may be associated with substantial adverse effects and high relapse rates. To determine whether CsA is effective for long-term remission in the treatment of IMN with moderate to high risk for progression to renal failure, when given in a dosage of 3.5 mg/kg/day for 18 months, then tapered gradually to a maintenance dose of 0.35-0.70 mg/kg/day within 6 months and continued for 5.5 years. METHODS The long-term effectiveness of our CsA regimen in 33 incident nephrotic IMN patients was determined retrospectively. Daily proteinuria, serum albumin and creatinine clearance were compared before starting therapy (time 0) and at 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 years. RESULTS At the end of 18 months, 84.8% of patients treated with CsA were in remission; 78.8% maintained long-term remission for 10 years. All patients with complete remission (CR), 75% of those with partial remission (PR), 20% of non-responders (NR) and 14.3% of those who were treated with NIST, were free of chronic kidney disease (CKD) stage 3 at 10 years (P<0.001). Reduction in daily proteinuria by ≥50% at 6 months was the most powerful predictor for achievement of CR or PR (P=0.02). CONCLUSIONS For most patients, CsA was effective in achieving sustained long-term remission without relapses, when gradually tapered to low maintenance dose given for 5.5 years.