OBJECTIVES: Evaluate rate of flares in adult SLE patients with active antinuclear autoantibody positive SLE disease and estimate the incremental direct costs of flare management. METHODS: A multi-centre retrospective chart review study extracting patient characteristics, disease activity and severity, and medical resource utilization in 5 European countries (France, Germany, UK, Italy and Spain). Patients were stratified by disease severity at inclusion visit (50% severe) and followed-up for 2 years. Severe disease defined as having at least one major domain actively involved (renal, neurological, cardiovascular or respiratory) and requiring >7.5 mg/day of corticosteroids and/or immunosuppressants.  A modification of SELENA-SLEDAI Flare Index collected retrospectively was used for identifying mild/moderate and severe flares. Unadjusted mean costs associated with management of flares were assessed. Health care perspective and country specific data was used for resources and costs analysis. RESULTS: The total sample included 427 SLE patients (212 severe, 215 non-severe), mean age: 43.4 years, female: 90.5%. Total mean number of flares over the study period was 2.29 compared to 1.83 (p<0.001) for severe and non-severe patients respectively. Mean number of mild/moderate flares was 0.87 compared to 1.32 (p<0.001), while mean number of severe flares was 1.42 compared to 0.52 (p<0.001) for severe and non-severe patients, respectively. The mean two year costs for patients experiencing at least one flare over study period was €9607 compared to €3910 (p<0.001) without flares.  Exploratory flare analysis showed a mean 2 year increase in costs of €4525 (p<0.01) per severe flare (no statistical significance for mild/moderate flares).   CONCLUSIONS: Severe patients experience both a higher number of flares and more severe flares compared to non-severe patients. Patients experiencing at least one flare over the study period are 2.5 times more costly than patients without flares; the presence of severe flares in SLE patients has a significant impact on the healthcare system.