Nursing education in the United Kingdom currently draws heavily upon Schon's concept of the reflective practitioner, and Benner's concept of the expert It is claimed that experienced practitioners are unable to articulate all they know, and that their knowledge is of a qualitatively different type from that learned by beginners Schön states that professional education gives privileged status to systematic, preferably scientific, knowledge, that technical knowledge drives out the artistry and competence of skilful practice, and that knowing that takes precedence over knowing how In the first part of this paper, various writers on the subject of expert, tacit knowledge are discussed Second, the paper examines the implications of expert knowledge for nursing research Certainly it may be considered a methodological headache, since if expert knowledge is tacit it cannot be researched by exclusively verbal methods such as questionnaires; open-ended discussion may be appropriate, or perhaps participant observation Nor will the findings be neat and easily analysed But tacit knowledge is also an untapped resource for co-operative enquiry between researcher and practitioner, and nursing research has an important role in enhancing the knowledge creation capacity of practitioners