To assess the prognostic significance of complete remission in patients with idiopathic membranous nephropathy, 33 patients were followed for a median of 96 months after remission of proteinuria. All patients had had a histological diagnosis of membranous nephropathy and a nephrotic syndrome. Only patients with a complete remission lasting for at least six months and with a follow-up of at least four years after remission were considered. No relapse of proteinuria developed in 17 patients (51%), 7 patients had relapse of non-nephrotic proteinuria (21%) and 9 (27%) relapse of nephrotic proteinuria. However proteinuria disappeared again in some patients so that at follow-up 73% of patients are in complete remission, 21% have non-nephrotic proteinuria and only 6% have nephrotic syndrome. All patients maintained a normal plasma creatinine over the years. It is concluded that complete remission of proteinuria is a strong predictor of long-term favourable outcome in patients with idiopathic membranous nephropathy.