Background and objectives ANCA-associated vasculitis is commonly found in elderly patients, but there are few data concerning outcome and treatment in the highest age groups.Design, setting, participants, & measurements Consecutive patients (N=151) presenting between 1997 and 2009 were retrospectively included from local registries in six centers in Sweden, the United Kingdom, and the Czech Republic if diagnosed with microscopic polyangiitis or granulomatosis with polyangiitis at age $75 years during the study period. Patients were followed until 2 years from diagnosis or death. Data on survival and renal function were analyzed with respect to age, sex, ANCA specificity, renal function, C-reactive protein, comorbidities, and Birmingham Vasculitis Activity Score at diagnosis as well as treatment during the first month.Results Median follow-up was 730 days (interquartile range, 244-730). Overall 1-year survival was 71.5% and 2-year survival was 64.6%. Older age, higher creatinine, and lower Birmingham Vasculitis Activity Score were associated with higher mortality in multivariable analysis. Patients who were not treated with standard immunosuppressive therapy had significantly worse survival. Renal survival was 74.8% at 1 year. No new cases of ESRD occurred during the second year. High creatinine at diagnosis was the only significant predictor of renal survival in multivariable analysis.Conclusions ANCA-associated vasculitis is a disease with substantial mortality and morbidity among elderly patients. This study showed a better prognosis for those who received immunosuppressive treatment and those who were diagnosed before having developed advanced renal insufficiency.