Whether and how treating idiopathic membranous nephropathy (IMN) is still a matter of debate. While there is general agreement that nonnephrotic patients should be given symptomatic treatment alone, the results of specific therapy addressed to interfere with direct or indirect causes of renal damage are controversial. There is no evidence in favour of therapies based on corticosteroids alone. A few old randomized controlled trials (RCT) reported that alkylating agents, cyclophosphamide and chlorambucil, may increase the probability of remission, but the prolonged use of these agents may cause disquieting adverse effects. RCT showed that a treatment based on alternating corticosteroids and a cytotoxic agent every other month for 6 months may favour remission of the nephrotic syndrome (NS) and may protect renal function in the long-term. More recently, good results have also been reported with synthetic adrenocorticotropic hormone (ACTH), cyclosporine, tacrolimus, mycophenolate mofetil (MMF), and rituximab. Unfortunately, however, most of the therapeutical attempts with these drugs have not been tested in controlled, randomized trials and the follow-up in these studies was generally short-time. Attempts of modifying the natural course of IMN have also been tried in patients with an established renal insufficiency. A number of patients showed improvement of proteinuria and renal function after treatments based on corticosteroids and cytotoxic drugs. However, in most responders the values of creatinine clearance did not return to normal and little information is available about the long-term follow-up of these patients.