The treatment of membranoproliferative glomerulonephritis (MPGN) is considered by most authors as unrewarding, and the disease progresses to end-stage renal disease (ESRD). We studied the effectiveness of a new immunosuppressive (IS) regimen by analyzing the rates of remission, relapse and progression to ESRD in 19 patients with MPGN. The treatment consisted of 4 phases: (1) induction with intravenous boluses of methylprednisolone plus cyclophosphamide (CPM) orally; (2) maintenance with oral prednisone (PDN) in an alternate-day regimen and CPM in a daily oral dose; (3) tapering during which PDN alone was slowly decreased; (4) discontinuation when CPM was omitted and PDN slowly withdrawn according to the steroid withdrawal schedule. At the end of the treatment that lasted on average 10 +/- 1 months, 15 patients remitted, 3 improved and 1 progressed. There were 8 relapses in 6 patients: 4 in 3 patients were treated with repeat cycles and remitted completely. Four patients who had relapsed after 4, 8, 11 and 13 years of remission refused retreatment and progressed rapidly to ESRD. All patients treated and retreated after relapsing had remissions, while renal failure and disease progression occurred in 1 patient only. Plasma creatinine averaged, in the whole group, 165 +/- 26 before, 156 +/- 30 after treatment and 224 +/- 57 microM/l at the end of 7.4 +/- 0.8 years of follow-up. An intensive IS regimen combining steroids and alkylating agents in high doses and for a prolonged time is effective in inducing remission and halting progression to ESRD in patients with MPGN.