Background: Current therapies for antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis are limited by toxicity. Objective: To compare pulse cyclophosphamide with daily oral cyclophosphamide for induction of remission. Design: Randomized, controlled trial. Random assignments were computer-generated; allocation was concealed by faxing centralized treatment assignment to providers at the time of enrollment. Patients, investigators, and assessors of outcomes were not blinded to assignment. Setting: 42 centers in 12 European countries. Patients: 149 patients who had newly diagnosed generalized ANCA-associated vasculitis with renal involvement but not immediately life-threatening disease. Intervention: Pulse cyclophosphamide, 15 mg/kg every 2 to 3 weeks (76 patients), or daily oral cyclophosphamide, 2 mg/kg per day (73 patients), plus prednisolone. Measurement: Time to remission (primary outcome); change in renal function, adverse events, and cumulative dose of cyclophosphamide (secondary outcomes). Results: Groups did not differ in time to remission (hazard ratio, 1.098 [95% CI, 0.78 to 1.55]; P = 0.59) or proportion of patients who achieved remission at 9 months (88.1% vs. 87.7%). Thirteen patients in the pulse group and 6 in the daily oral group achieved remission by 9 months and subsequently had relapse. Absolute cumulative cyclophosphamide dose in the daily oral group was greater than that in the pulse group (15.9 g [interquartile range, 11 to 22.5 g] vs. 8.2 g [interquartile range, 5.95 to 10.55 g]; P <0.001). The pulse group had a lower rate of leukopenia (hazard ratio, 0.41 [CI, 0.23 to 0.71]). Limitations: The study was not powered to detect a difference in relapse rates between the 2 groups. Duration of follow-up was limited. Conclusion: The pulse cyclophosphamide regimen induced remission of ANCA-associated vasculitis as well as the daily oral regimen at a reduced cumulative cyclophosphamide dose and caused fewer cases of leukopenia. Primary Funding Source: The European Union.