Background: This study is aimed at providing a real-world evaluation of the economic cost of persistent asthma among European adults according to the degree of disease control [as defined by the 2006 Global Initiative for Asthma (GINA) guidelines]. Methods: A prevalence-based cost-of-illness study was carried out on 462 patients aged 30-54 years with persistent asthma (according to the 2002 GINA definition), who were identified in general population samples from 11 European countries and examined in clinical settings in the European Community Respiratory Health Survey II between 1999 and 2002. The cost estimates were computed from the societal perspective following the bottom-up approach on the basis of rates, wages and prices in 2004 (obtained at the national level from official sources), and were then converted to the 2010 values. Results: The mean total cost per patient was EUR 1,583 and was largely driven by indirect costs (i.e. lost working days and days with limited, not work-related activities 62.5%). The expected total cost in the population aged 30-54 years of the 11 European countries was EUR 4.3 billion (EUR 19.3 billion when extended to the whole European population aged from 15 to 64 years). The mean total cost per patient ranged from EUR 509 (controlled asthma) to EUR 2,281 (uncontrolled disease). Chronic cough or phlegm and having a high BMI significantly increased the individual total cost. Conclusions: Among European adults, the cost of persistent asthma drastically increases as disease control decreases. Therefore, substantial cost savings could be obtained through the proper management of adult patients in Europe.