Retroperitoneal fibrosis (RPF) is an inflammatory disorder that affects the infrarenal great vessels and surrounding structures. Although first described in 1948 by Ormond, much of the information currently available on this disease is conflicting and results from multiple definitions used by different investigators. We conducted the current study to describe the clinical, laboratory, and radiographic presentation of RPF from a single center using data collected in a prospective fashion.Data on all patients who were referred to our RPF clinic were prospectively collected. We obtained information on presenting signs and symptoms, and on the presence or absence of "traditional risk factors," comorbidities, and family histories. All patients underwent the same battery of laboratory testing, including complete blood count, renal function profile, erythrocyte sedimentation rate (ESR), thyroid-stimulating hormone, and antinuclear antibodies (ANA). All patients had contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI) of the abdomen and pelvis. The extent of disease was classified based on the anatomic location of the soft-tissue density.Forty-eight patients (26 male and 22 female) met the criteria for RPF and were included in the study. The mean age was 54.25 years. Few patients had traditional risk factors for RPF. Pain and weight loss were the most common presenting symptoms. The mean hemoglobin was 11.6 g/dL. The mean ESR was 40.5 mm/h. Nine patients had positive ANA, all with negative antibodies to dsDNA. CT or MRI revealed the presence of a periaortic soft-tissue density in all (100%) patients; 69% had pericaval involvement, 62% had obstruction of 1 or both ureters, and 35% of patients had involvement of the renal artery or renal vein.In the current report we present the demographics and laboratory and radiographic presentation of a homogenous group of patients with RPF. We attempt to solidify a proper scheme of classification for the disease, and suggest an anatomic classification system that may be used for future studies.