We report on a patient with an almost 20-year history of B chronic lymphocytic leukemia (B-CLL). During the last 2 years, the patient developed nephrotic syndrome (NS) due to membranous glomerulonephritis (MN), refractory to standard therapeutic regimens. Neither NS nor B-CLL responded objectively to systemic administration of two different combinations of corticosteroids and alkylating agents (chlorambucil, cyclophosphamide). Third-line therapy with cyclosporin A resulted in reduction of proteinuria and improvement of leukemia. Withdrawal of the drug led to an increase in leukocyte count.