Abstract
External assurance provides higher credibility to Corporate Social Responsibility (CSR) reports. This paper looks into 2.685 CSR reports by European companies during 2005- 2009 to identify assurance trends. Our results confirm that the assurance decision depends on certain variables such as company size, industry, year and accounting system of countries.Spain, with 33% of assurance reports, is the country with more CSR reports assured, being a global leader as regards the search for higher quality in the social and environmental reporting practice.