Abstract : The article provides an overview on the definition and evolution of grey literature (GL) in the emerging environment of online resources and open access to scientific and technical information. First, it gives some empirical evidence on the importance of GL in scientific publications from different domains, especially education, based on citation analysis. Other topics: the impact of Internet on the production of GL, the place of grey resources in open archives and institutional repositories, the development of bibliographic control and standardization of GL and the difficulties of identification and accessing of grey documents. The article ends with some prognostics on the future of GL and open questions for research in library and information sciences on GL. Based on an article first published in French in Perspectives Documentairses en Education 2006, n° 62.