BACKGROUND: The risk of early death is particularly high in patients over the age of 65 presenting with antineutrophil cytoplasmic antibody (ANCA)-associated renal vasculitis. We hypothesized that by combining disease severity markers, a comorbidity index and serious adverse event reports, we would be able to identify early predictors of one-year mortality in this population. METHODS: We performed a multicentre, retrospective study in the nephrology and internal medicine departments of six tertiary hospitals in northern France. A total of 149 patients (median [interquartile range (IQR)] age: 72.7 [68.5-76.8] years) presenting with ANCA-associated vasculitis and renal involvement were included between January 2002 and June 2015. The primary endpoint was the one-year mortality rate. RESULTS: Renal function was severely impaired at presentation (median [IQR] peak serum creatinine (SCr): 337 [211-522] μmol/l), and 45 patients required dialysis. The Five-Factor Score (FFS, scored as + 1 point for each poor prognostic factor (age > 65 years, cardiac symptoms, gastrointestinal involvement, SCr ≥150 μmol/L, and the absence of ear, nose, and throat involvement)) was ≥3 in 120 cases. The one-year mortality rate was 19.5%. Most of the deaths occurred before month 6, and most of these were related to severe infections. In a univariate analysis, age, a high comorbidity index, a performance status of 3 or 4, a lack of co-trimoxazole prophylaxis, early severe infection, and disease activity parameters (such as the albumin level, haemoglobin level, peak SCr level, dialysis status, and high FFS) were significantly associated with one-year mortality. In a multivariable analysis, the best predictors were a high FFS (relative risk (RR) [95% confidence interval (CI)] = 2.57 [1.30-5.09]; p = 0.006) and the occurrence of a severe infection during the first month (RR [95%CI] = 2.74 [1.27-5.92]; p = 0.01). CONCLUSIONS: When considering various disease severity markers in over-65 patients with ANCA-associated renal vasculitis, we found that an early, severe infection (which occurred in about a quarter of the patients) is a strong predictor of one-year mortality. A reduction in immunosuppression, the early detection of infections, and co-trimoxazole prophylaxis might help to reduce mortality in this population.