Interferon-alpha (IFN-alpha) is a naturally occurring cytokine. It was the first cytokine used with clinical benefit in the treatment of viral hepatitis and malignancies. Patients with viral hepatitis B or C may have complications with glomerulonephritis (GN). Improvement in proteinuria with or without clearing of viral markers after IFN-alpha therapy has been reported. This encouraged us to offer IFN-alpha therapy to four patients with GN. These patients refused treatment with steroids and/or cyclophosphamide because of concerns about side effects. One patient with membranous GN and two patients with mesangial GN (MesGN) had a remission of nephrotic syndrome. In one patient with type II diabetes and MesGN, renal insufficiency and proteinuria did not subside; however, renal function remained stable. The mechanism of action of IFN-alpha is discussed, with its possible role in the treatment of primary GN.