Introduction. The question of credibility in participatory information environments, particularly Wikipedia, has been much debated. This paper investigates how editors on Swedish Wikipedia consider credibility when they edit and read Wikipedia articles. Method. The study builds on interviews with 11 editors on Swedish Wikipedia, supported by a document analysis of policies on Swedish Wikipedia. Analysis. The interview transcripts have been coded qualitatively according to the participants' use of Wikipedia and what they take into consideration in making credibility assessments. Results. The participants use Wikipedia for purposes where it is not vital that the information is correct. Their credibility assessments are mainly based on authorship, verifiability, and the editing history of an article. Conclusions. The situations and purposes for which the editors use Wikipedia are similar to other user groups, but they draw on their knowledge as members of the network of practice of wikipedians to make credibility assessments, including knowledge of certain editors and of the MediaWiki architecture. Their assessments have more similarities to those used in traditional media than to assessments springing from the wisdom of crowds.