Background: Immunosuppressive therapy has improved the outcome of ANCA-associated vasculitis (AAV), but infectious morbidity and mortality remained high. Recognizing its risk factors seems crucial for prevention, aiming to increase survival of these patients. Methods: We investigated the incidence and types of infections and assessed predictive factors in 132 patients with severe systemic AAV. Results: Patients with lower than median incidence of total infections/patient-year during induction had lower baseline serum creatinine, dialysis requirement and Charlson comorbidity index (CCI), compared to those with higher than median incidence (P 5 0.037; P 5 0.024; P 5 0.001; respectively). In subgroups with below and above than median number of severe infections/patient-year during induction, differences were found in baseline creatinine (P 5 0.002) and dialysis requirement (P 5 0.001); comparing the same cohorts during maintenance immunosuppression, baseline dialysis requirement, diabetes, CCI, and dose of cyclophosphamide (CYC) administered as induction therapy differed significantly (P 5 0.019; P 5 0.015; P 5 0.001; P 5 0.015, respectively). Severe infections were predicted by baseline serum creatinine (OR 1.002 [CI 1.001-1.003]) and pulmonary manifestation (OR 2.153 [CI 1.017-4.560]) during induction immunosuppression. In multivariable Cox regression model all-cause mortality was independently predicted by severe infection (HR 1.998 [CI 1.214-3.287]). Among the 168 positive cultures Gram-negative bacteria were responsible for blood stream infections in 33%, and respiratory tract infections in 72%. Conclusions: Advanced renal failure, pulmonary involvement and high degree of comorbidities increase the risk of infection in AAV. Those who suffer infection during induction immunosuppression have worse long-term survival. Our findings indicate the need for high vigilance for infections and close follow-up of comorbidities when treating AAV.  Kulcsszavak: ANCA-associated vasculitis, comorbidity, immunosuppression, infections, mortality, survival