PURPOSE: Idiopathic retroperitoneal fibrosis (IRPF) is an unusual progressive illness for which consistent therapeutic recommendations have not been devised. The present report describes a collaborative nephrology and urology approach to distinguish IRPF from secondary disease and then combine necessary acute surgical or radiological intervention with short-term corticosteroid and with mycophenolate mofetil (MM) to facilitate steroid tapering and long-term management. MATERIALS AND METHODS: 21 patients have been evaluated and followed over a 7-year period, 16 with characteristic IRPF and 5 with secondary retroperitoneal disease. IRPF patients initially received high-dose corticosteroid and MM. We report clinical follow-up along with imaging studies of the retroperitoneum and related organs, serologic markers for systemic disease, and nonspecific acute-phase reactants as indicators of ongoing disease activity. RESULTS: Among IRPF patients, uniform success in stabilizing clinical signs and symptoms, radiological disease in the retroperitoneum and associated organs, and inflammatory indicators have been observed. Corticosteroid therapy can be limited to 6 months or less and MM to approximately 2 years, all with substantial impact on the natural history of IRPF. CONCLUSIONS: This is not a randomized, controlled trial, and patients were often referred with prior complications and/or treatments, however, the systematic approach and consistent results support the utility of MM as a safe and effective choice for long-term stabilization in IRPF.