The use of the term 'expert' occurs widely in healthcare research, in the context of national guidelines and consensus methods for the development of clinical protocols. Within consensus methods of research, especially Delphi panel techniques, the use of 'experts' is fundamental to reliability. Yet literature fails to debate the practicalities of defining 'experts' for use within Delphi panel research. This paper, by John Baker and colleagues, draws on methodological literature and discusses the concepts and elements of 'experts'. It concludes with recommendations for researchers to ensure experts for future Delphi research.