Glucocorticoids, cytostatic agents and cyclosporin are frequently employed in the treatment of glomerular diseases of immunologic origin. In order to assess the efficacy of these drugs, we retrieved--with the help of a Medline-based search--and analysed all controlled studies published since 1966 dealing with immunosuppressive therapy of glomerulonephritis. Of the 34 identified controlled studies, only 27 had a prospective and randomized design. In patients with minimal-change glomerulonephritis, proteinuria decreases and disappears during therapy with prednisone. A comparable effect can be obtained with cyclosporin. Occasionally, there is a relapse of proteinuria after cessation of the immunosuppressive therapy in some patients. These relapses can be controlled with a chlorambucil-based regimen. Chlorambucil may be successfully utilized in the treatment of focal-segmental glomerulosclerosis, a form of glomerulonephritis which is more refractory to glucocorticoid therapy and is probably pathogenetically related to minimal-change glomerulonephritis. Patients with membranous glomerulonephritis and a nephrotic syndrome seem to benefit from an alternate month prednisone and chlorambucil regimen. However, an indiscriminate treatment of all patients with this regimen is not legitimate, because some patients would be overtreated as the disease may undergo spontaneous remission. There are no well-documented valuable therapies for the IgA-associated glomerulonephritis and the membranoproliferative glomerulonephritis. The combination of prednisone with cytotoxic substances, particularly cyclophosphamide and azathioprine, seem to remarkably improve the renal prognosis of the diffuse proliferative lupus glomerulonephritis. The efficacy of cyclophosphamide and prednisone with or without plasma exchange in the treatment of the rapidly progressive glomerulonephritis due to other systemic diseases (M. Wegener, panarteritis nodosa, Goodpasture syndrome) is a widely accepted therapeutic modality, although controlled studies are lacking. Immunosuppressive therapy of glomerulonephritis bears notable risks and sometimes questionable efficacy. Thus, before prescribing any immunosuppressive therapy, it is mandatory to evaluate in every single patient the prognostic factors of the underlying disease, the probability of the onset of severe side effects and the possible acceptance of a renal replacement therapy, including renal transplantation.