Abstract: The IQWiG Non-Drug Interventions Working Group are: Scheibler F., Buenemann A.,Felgentraeger K., Grosselfinger R., Herrmann-Frank A., Hommerich J., Koch K., Kreis J., Scheike I., Kulig M. Background: Wikipedia is going head to head with major encyclopaedias for several topics. Its value in the field of evidence-based medicine (EBM) has not been evaluated so far. Objectives: The aim of this study was to investigate the usefulness of Wikipedia for EBM. Methods: We selected 100 of the 520 terms and definitions from the glossary of The Cochrane Collaboration website as a reference standard. First, we investigated whether definitions of these terms could be retrieved in the web glossaries of the German Cochrane Centre, the German network for EBM and the English and German Wikipedia sites. Second, we compared the retrieved definitions to those of the reference standard applying four categories: (1) missing, (2) identical/similar, (3) identical/similar with additional information or (4) not useful/misleading. Results: About one quarter of the definitions were identical or very similar to the reference glossary in all four sources. While more than half of the definitions were missing in the German glossaries, only a quarter and a sixth of the definitions could not be found in the German and English Wikipedia, respectively. Furthermore, for more than a quarter of the terms useful additional information was found in the Wikipedias. However, about one quarter of the terms in both Wikipedias were evaluated as not useful for EBM or even misleading. Although ratings of each term were given independently by two of the authors and disagreements were resolved by discussion, they might be subjective. It should also be considered that all sources used are internet-based and might change over time. Conclusions: This exploratory ‘validation’ of the Wikipedia and German EBM sources shows that none of them reaches the completeness of the CC glossary. Compared to the CC glossary, the usefulness of the definitions of EBM terms in Wikipedia is limited. People working in the field of EBM might consider becoming involved in editing Wikipedia.