The use of critical appraisal guidelines to assess the validity of research findings has become an established technique in those disciplines, such as healthcare and medicine, that encourage the use of evidence-based practice. Critical appraisal guidelines provide a rigorous set of criteria, often in the form of a checklist, against which a piece of research can be assessed. Although well established criteria exist for many forms of quantitative research, such as clinical trials and cohort studies, qualitative research is less well served. Through a synthesis of existing best practices in interpretative research this paper provides comprehensive guidelines for the conduct of single case study research and extrapolates from them a set of critical appraisal guidelines to assist in the evaluation of such work.