Background: Anti-neutrophil cytoplasm antibodies (ANCA) may be pathogenic in ANCA- associated vasculitis. Rapid removal of ANCA by plasma exchange as an adjuvant to immune suppression and glucocorticoids may prevent progressive disease resulting in end-stage renal disease and death. Methods: We performed an open-label, 2-by-2 factorial randomized trial to separately evaluate plasma exchange and two regimens of oral glucocorticoids in patients with severe ANCA-associated vasculitis defined by glomerular filtration rate < 50ml/min or diffuse lung hemorrhage or both. To evaluate plasma exchange, participants were randomly assigned to either 7 plasma exchanges in 14 days or no plasma exchange. All patients received intravenous glucocorticoids and a tapering course of oral glucocorticoids, with cyclophosphamide or rituximab. Patients were followed up to 7 years for the primary composite outcome of death from any cause or end-stage renal disease. Results: The primary outcome occurred in 100 of 352 patients (28.4%) in the plasma exchange group and 109 of 352 patients (30.9%) in the control group (hazard ratio 0.86, 95% confidence interval [CI] 0.65 to 1.13; p = 0.27). No benefits were detected for either component of the primary outcome (hazard ratio for death 0.87, 95% CI 0.59 to 1.29 and for end-stage renal disease 0.81, 95% CI 0.57 to 1.13). There was no evidence of benefit in any pre-defined subgroup. Sixty-four percent of patients in both groups experienced at least one serious adverse event. Conclusion: Plasma exchange did not reduce the risk of death or end-stage renal disease in patients with severe ANCA-associated vasculitis. Disclosures: National Institute for Health Research (UK): HTA 08/56/04; Food and Drug Administration/National Institutes of Health (USA): FDA R01 FD003516 and the National Institutes of Health (USA) - National Institute of Arthritis and Musculoskeletal and Skin Diseases: U54 AR0573319; National Health and Medical Research Council (Australia): 626939; National Health and Medical Research Council (Australia): APP1086192; National Health and Medical Research Council (Australia): 631731; National Health and Medical Research Council (Australia): APP1092957; Canadian Institutes of Health Research (Canada): 211079; Canadian Institutes of Health Research (Canada): 159662, French Ministry of Health Programme Hospitalier de Recherche Clinique (France): AOM11142, Research Committee on Intractable Vasculitides, the Ministry of Health, Labour and Welfare of Japan; and The Japan Agency for Medical Research and Development (AMED): The Strategic Study Group to Establish the Evidence for Intractable Vasculitis Guideline (Japan); TermuoBCT, TerumoBCT Mexico, Fresenius Medical Care Australia, Baxter Healthcare Pty Ltd (Australia), and Asahi Kasei Medical Co., Ltd. provided in-kind plasma exchange disposables.